Copper alloy

ABSTRACT

A copper alloy according to the present invention includes 17 mass % to 34 mass % of Zn, 0.02 mass % to 2.0 mass % of Sn, 1.5 mass % to 5 mass % of Ni, and a balance consisting of Cu and unavoidable impurities, in which relationships of 12≤f1=[Zn]+5×[Sn]−2×[Ni]≤30, 10≤[Zn]−0.3×[Sn]−2×[Ni]≤28, 10≤f3={f1×(32−f1)×[Ni]} 1/2 ≤33, 1.2≤0.7×[Ni]+[Sn]≤4, and 1.4≤[Ni]/[Sn]≤90 are satisfied, conductivity is 13% IACS to 25% IACS, a ratio of an α phase is 99.5% or more by area ratio or an area ratio of a γ phase (γ)% and an area ratio of a β phase (β)% in an α phase matrix satisfy a relationship of 0≤2×(γ)+(β)≤0.7.

TECHNICAL FIELD

The present invention relates to a copper alloy (Cu—Zn alloy, that is,brass) which has a brass-yellow color, and has stress corrosion crackingresistance, color fastness, antimicrobial properties, excellent stressrelaxation characteristics, strength, and bending workability.Particularly, the present invention relates to a copper alloy used forapplications such as terminals and connectors for automobiles,electronic and electrical apparatuses, medical appliances, public usesuch as handrails, door handles, and water supply and drain sanitaryfacilities, and construction-related use.

Priority is claimed on Japanese Patent Application No. 2013-199475,filed Sep. 26, 2013, and Japanese Patent Application No. 2014-039679,filed Feb. 28, 2014, the contents of which are incorporated herein byreference.

BACKGROUND ART

In the related art, brass (Cu—Zn alloy) having Cu and Zn as maincomponents has been used for constituent materials for connectors,terminals, relays, springs, sockets, switches, and the like which areused in decoration members such as handrails, door handles, lightingequipment, elevator panels, and the like, construction members, metalfittings and metal goods, or electronic and electrical components,automobile components, communication apparatuses, electronic andelectrical apparatuses, and the like. However, under high temperatureand high humidity conditions, the color of the brass is changed due tosurface oxidation for a short period of time even in a room. As aresult, the brass-yellow color is impaired, which causes a problem inappearance. When a transparent clear coating or Ni or Sn plating iscarried out to avoid a color change, the antimicrobial performance andthe conductivity of the copper alloy are not exhibited in some cases.

In recent years, along with a reduction in size and weight and highperformance of apparatuses, connectors, terminals and the like have beenrequired to have extremely strict characteristic improvements and costperformance. For example, a thin sheet is used for a spring contactportion of a connector. However, it is required for a high strengthcopper alloy which constitutes the thin sheet to have high strength, ahigh degree of balance between elongation and strength, and resistanceto severe use environments, that is, excellent color fastness, stresscorrosion cracking resistance, and stress relaxation characteristics soas to realize a small thickness. Further, it has been required to obtainhigh productivity, particularly, to obtain excellent economicalefficiency by keeping the amount of copper used which is a noble metalto a minimum.

Examples of the above-described use environment of the copper alloyinclude an indoor environment (including the inside of a car) at a hightemperature or a high humidity, an environment in which a large numberof unspecified people touch the alloy, and an environment including asmall amount of a nitrogen compound such as ammonia and amine, and thelike. The copper alloy is required to have color fastness and stresscorrosion cracking resistance to endure these environments.

In handrails, door handles, unplated connectors, terminals and doorhandles, and the like, there arise not only problems in appearance andstress corrosion cracking, but also problems of deterioration inantimicrobial properties and conductivity due to oxidation of thesurface of brass.

Further, connectors, terminals and the like are used in a cabin of anautomobile and a portion close to an engine room under the blazing sunand in this case, the temperature in the use environment reaches about100° C. High material strength is required in the case in which thethickness of the material has to be reduced. When a copper alloy is usedfor terminals and connectors, high material strength is required toobtain high contact pressure. However, in the applications for springs,terminals and connectors, the high material strength can be used withina range of stress of the elastic limit at room temperature. However, asthe temperature rises in the use environment, for example, when thetemperature rises to 90° C. to 150° C. as described above, a copperalloy is permanently deformed. Particularly, in the case of brass, adegree of permanent deformation is great and a predetermined contactpressure cannot be obtained. In order to utilize high strength, a smalldegree of permanent deformation at a high temperature is demanded and itis preferable that the properties called stress relaxationcharacteristics are excellent as the measure of the degree of permanentdeformation at a high temperature.

However, the plating layer on the surface of a plated product is peeledoff by long term use. In addition, when a large amount of products suchas connectors or terminals are produced at low costs, in a process ofproducing a sheet which becomes a material thereof, the surface of thesheet is plated with Sn, Ni and the like in advance and the sheetmaterial is punched and used. In this case, the punched surface is notplated with Sn, Ni and the like and thus color change or stresscorrosion cracking easily occurs. Further, when Sn, Ni and the like areincluded in the plating according to the kind of the plating, it isdifficult to recycle the copper alloy.

Here, examples of a high strength copper alloy include phosphor bronze(Cu-6 mass % to 8 mass % Sn—P), and nickel silver (Cu—Zn-10 mass % to 18mass % Ni). As a general copper alloy which has excellent costperformance and high conductivity and high strength, generally, brass iswell-known.

In Patent Document 1, as an alloy which satisfies the requirements forhigh strength, a Cu—Zn—Sn alloy is disclosed.

On the other hand, constituent members such as side rails, headboards,footboards, handrails, door handles, door knobs, door levers, andmedical appliances used in medical institutions, public facilities,facilities and equipment corresponding to these medical institutions andpublic facilities, and research facilities for strict hygiene management(for example, food, cosmetics, pharmaceutical products and the like),and water supply and drain sanitary facilities and apparatuses such as adrainage tank used in vehicles and the like are formed by joining pipes,sheets, strips, rods, castings, and members formed to have variousshapes by forging.

Here, in the case of welding a copper alloy including Zn, since Zneasily evaporates during the welding, a technique is required forwelding. In addition, the welding leaves a bead trace in appearance andin order to solve a problem in appearance, a process of polishing a beadtrace is added. Depending on the shape, it may be difficult to removethe bead trace completely. Then, there arises a problem in appearanceand it takes much time to remove the bead trace. Thus, this case is notpreferable. Further, there is a concern of antimicrobial properties(bactericidal properties) being deteriorated.

In order to obtain sufficient antimicrobial properties (bactericidalproperties), instead of joining copper alloy members, a method ofattaching a thin copper foil or a composite material obtained by bondinga copper foil and a resin or paper to constituent members such ashandrails, door handles, door knobs, and door levers has been attempted(for example, refer to Patent Document 2).

RELATED ART DOCUMENT Patent Document

[Patent Document 1] JP-A-2007-056365

[Patent Document 2] JP-A-11-239603

SUMMARY OF THE INVENTION Problem that the Invention is to Solve

However, the above-described general high strength copper alloys such asphosphor bronze, nickel silver and brass have the following problems andcannot respond to the above-described requirements.

Since phosphor bronze and nickel silver have poor hot workability andare difficult to be produced by hot rolling, phosphor bronze and nickelsilver are generally produced by horizontal continuous casting.Therefore, the productivity is poor, the energy cost is high, and theyield is also poor. In addition, since a large amount of copper, whichis a noble metal, is contained in phosphor bronze and nickel silver orlarge amounts of expensive Sn and Ni are contained in phosphor bronzeand nickel silver, there is a problem in economic efficiency, and bothhave poor conductivity. Since the specific gravities of these alloys areas high as about 8.8, there arises a problem of weight reduction. Nickelsilver containing 10 mass % or more of Ni and phosphor bronze containing8 mass % or more of Sn have high strength. However, nickel silver has aconductivity of 10% IACS or less and phosphor bronze has a conductivityof 13% IACS or less. Both have low conductivity and this lowconductivity causes a problem in use.

Brass containing 20 mass % to 35 mass % of Zn is inexpensive. However,the color is easily changed, stress corrosion cracking easily occurs,and brass is easily affected by heat. That is, brass has a fatal defectof poor stress relaxation characteristics and is not satisfactory interms of strength and balance between strength and bending. Brass is notsuitable for a constituent member of a product for realizing a reductionin size and high performance as described above. Particularly, phosphorbronze and brass have a problem in color fastness and are used by beingplated with Sn, Ni or the like in many cases.

Specifically, in a Cu—Zn alloy, as a Zn content increases, the stresscorrosion cracking resistance deteriorates. When the Zn content is morethan 15 mass o, a problem arises. When the content is more than 20 mass% and is further more than 25 mass %, the stress corrosion crackingresistance deteriorates. When the content is 30 mass %, the sensitivityfor stress corrosion cracking is excessively increased and a seriousproblem arises. The stress relaxation characteristics are furtherimproved when the amount of Zn added is 3 mass % to 15 mass %. However,when the Zn content is more than 20 mass %, particularly, is more than25 mass %, the stress relaxation characteristics rapidly deteriorate.For example, when the content is 30 mass %, the stress relaxationcharacteristics are very poor. As the Zn content increases, the strengthis improved but the ductility and bending workability deteriorate.Further, the balance between strength and ductility deteriorates. Inaddition, the color fastness is poor irrespective of the Zn content andwhen the use environment is poor, the color of the alloy changes tobrown or red.

Accordingly, these high strength copper alloys cannot possibly besatisfactory as component constituent materials for various apparatusesthat tend to have high reliability with respect to the use environment,excellent cost performance, and realize reduction in size and weight andhigh performance, and development of a new high strength copper alloyhas been strongly demanded.

In addition, the Cu—Zn—Sn alloy described in Patent Document 1 does nothave sufficient characteristics including strength.

Further, as described in Patent Document 2, in the case of attaching acopper foil to the surface of the constituent member, due to a smallthickness of the copper foil, there is a concern of physical breakage orbreakage occurring according to the use environment. In addition, thereis a concern of peeling off of the copper coil from the constituentmember due to deterioration of an adhesive over time. The copper foilalso has a problem in color fastness and cannot always maintainantimicrobial properties (bactericidal properties) and color fastness.Furthermore, a problem of lowering of the strength of the joint portionof the constituent member cannot be solved by these methods.

The present invention has been made to solve the above-describedproblems in the related art, and an object thereof is to provide acopper alloy which has excellent cost performance, a small density,conductivity higher than the conductivity of phosphor bronze and nickelsilver, high strength, balance between strength and elongation andbending workability, excellent stress relaxation characteristics, stresscorrosion cracking resistance, color fastness and antimicrobialproperties, and is adaptable to various use environments.

Means for Solving the Problem

The present inventors have conducted various studies and experimentsfrom different angles to solve the above problems and have obtained thefollowing findings.

First, appropriate amounts of Ni and Sn are added to a Cu—Zn alloyincluding a high concentration of Zn of 34 mass % or less. In order tooptimize an interaction between Ni having a bivalent atomic valence (orvalence electron number) and Sn having a tetravalent atomic valence, thetotal content of Ni and Sn and a ratio of the contents of Ni and Sn areadjusted that is, 0.7×[Ni]+[Sn] and [Ni]/[Sn] are adjusted to be withinappropriate ranges. Further, the contents of Zn, Ni and Sn are adjustedin consideration of an interaction among Zn, Ni and Sn such that threerelational expressions of f1=[Zn]+5×[Sn]−2×[Ni, f2=[Zn]−0.3×[Sn]−2×[Ni],and f3={f1×(32−f1)×[Ni]}^(1/2) have appropriate values.

A metallographic structure that is basically composed of an a singlephase, in which at least, the ratio of an a phase in the constituentphase of the metallographic structure is 99.5% or more by area ratio (ina seam welded pipe, a welded pipe, brazing or the like, even when a basemetal is locally melted or heated to a high temperature, at three sitesof a joint portion or a melt zone, a heat affected zone, and a basemetal, the average ratio of the a phase in the constituent phase of themetallographic structure is 99.5% or more by area ratio), or ametallographic structure, in which an area ratio of a γ phase (γ)% andan area ratio of a β phase (β)% of an α phase matrix satisfy arelationship of 0≤2×(γ)+(β)≤0.7, and the γ phase having an area ratio of0% to 0.3% and the β phase having an area ratio of 0% to 0.5% aredispersed in the α phase matrix is provided.

Thus, a copper alloy which has excellent cost performance, a smallspecific gravity, excellent color fastness, high strength, excellentbalance among strength, elongation and bending workability andconductivity, excellent stress relaxation characteristics, excellentstress corrosion cracking resistance, and excellent antimicrobialproperties, and is adaptable to various use environments has been foundand the present invention has been completed.

Particularly, in the case of applications such as terminals andconnectors, in consideration of use in a high temperature environment,the metallographic structure was set to have an α single phase. Inaddition, P having a pentavalent atomic valence was incorporated and theratio of the P content and the Ni content was adjusted to be within anappropriate range. Thus, further excellent stress relaxationcharacteristics could be obtained.

According to a first aspect of the present invention, there is provideda copper alloy including: 17 mass % to 34 mass % of Zn; 0.02 mass % to2.0 mass % of Sn; 1.5 mass % to 5 mass % of Ni; and a balance consistingof Cu and unavoidable impurities, in which a Zn content [Zn] (mass %), aSn content [Sn] (mass %), and a Ni content [Ni] (mass %) satisfyrelationships of

12≤f1=[Zn]+5×[Sn]−2×[Ni]≤30,

10≤f2=[Zn]−0.3×[Sn]−2×[Ni]≤28, and

10≤f3={f1×(32−f1)×[Ni]}^(1/2)≤33,

the Sn content [Sn] (mass %) and the Ni content [Ni] (mass %) satisfyrelationships of

1.2≤0.7×[Ni]+[Sn]≤4, and

1.4≤[Ni]/[Sn]≤90,

conductivity is 13% IACS or more and 25% IACS or less, and in ametallographic structure, a ratio of an a phase in a constituent phaseof the metallographic structure is 99.5% or more by area ratio or anarea ratio of a γ phase (γ)% and an area ratio of a β phase (β)% of an αphase matrix satisfy a relationship of 0≤2×(γ)+(β)≤0.7, and the γ phasehaving an area ratio of 0% to 0.3% and the β phase having an area ratioof 0% to 0.5% are dispersed in the α phase matrix.

According to a second aspect of the present invention, there is provideda copper alloy including: 18 mass % to 33 mass % of Zn; 0.2 mass % to1.5 mass % of Sn; 1.5 mass % to 4 mass % of Ni; and a balance consistingof Cu and unavoidable impurities, in which a Zn content [Zn] (mass %), aSn content [Sn] (mass %), and a Ni content [Ni] (mass %) satisfyrelationships of

15≤f1=[Zn]+5×[Sn]−2×[Ni]≤30,

12≤f2=[Zn]−0.3×[Sn]−2×[Ni]≤28, and

10≤f3={f1×(32−f1)×[Ni]}^(1/2)≤30,

the Sn content [Sn] (mass %) and the Ni content [Ni] (mass %) satisfyrelationships of

1.4≤0.7×[Ni]+[Sn]≤3.6, and

1.6≤[Ni]/[Sn]≤12,

conductivity is 14% IACS or more and 25% IACS or less, and ametallographic structure is composed of an a single phase.

According to a third aspect of the present invention, there is provideda copper alloy including: 17 mass % to 34 mass % of Zn; 0.02 mass % to2.0 mass % of Sn; 1.5 mass % to 5 mass % of Ni; at least one or moreselected from 0.003 mass % to 0.09 mass % of P, 0.005 mass % to 0.5 mass% of Al, 0.01 mass % to 0.09 mass % of Sb, 0.01 mass % to 0.09 mass % ofAs, and 0.0005 mass % to 0.03 mass % of Pb; and a balance consisting ofCu and unavoidable impurities, in which a Zn content [Zn] (mass %), a Sncontent [Sn] (mass %), and a Ni content [Ni] (mass %) satisfyrelationships of

12≤f1=[Zn]+5×[Sn]−2×[Ni]≤30,

10≤f2=[Zn]−0.3×[Sn]−2×[Ni]≤28, and

10≤f3={f1×(32−f1)×[Ni]}^(1/2)≤33,

the Sn content [Sn] (mass %) and the Ni content [Ni] (mass %) satisfyrelationships of

1.2≤0.7×[Ni]+[Sn]≤4, and

1.4≤[Ni]/[Sn]≤90,

conductivity is 13% IACS or more and 25% IACS or less, and in ametallographic structure, a ratio of an a phase in a constituent phaseof the metallographic structure is 99.5% or more by area ratio or anarea ratio of a γ phase (γ)% and an area ratio of a β phase (β)% of an αphase matrix satisfy a relationship of 0≤2×(γ)+(β)≤0.7, and the γ phasehaving an area ratio of 0% to 0.3% and the β phase having an area ratioof 0% to 0.5% are dispersed in the α phase matrix.

According to a fourth aspect of the present invention, there is provideda copper alloy including: 18 mass % to 33 mass % of Zn; 0.2 mass % to1.5 mass % of Sn; 1.5 mass % to 4 mass % of Ni; 0.003 mass % to 0.08mass % of P; and a balance consisting of Cu and unavoidable impurities,in which a Zn content [Zn] (mass %), a Sn content [Sn] (mass %), and aNi content [Ni] (mass %) satisfy relationships of

15≤f1=[Zn]+5×[Sn]−2×[Ni]≤30,

12≤f2=[Zn]−0.3×[Sn]−2×[Ni]≤28, and

10≤f3={f1×(32−f1)×[Ni]}^(1/2)≤30,

the Sn content [Sn] (mass %) and the Ni content [Ni] (mass %) satisfyrelationships of

1.4≤0.7×[Ni]+[Sn]≤3.6, and

1.6≤[Ni]/[Sn]≤12,

the Ni content [Ni] (mass %) and the P content [P] (mass %) satisfy arelationship of

25≤[Ni]/[P]≤750,

conductivity is 14% IACS or more and 25% IACS or less, and ametallographic structure is composed of an a single phase.

According to a fifth aspect of the present invention, there is provideda copper alloy including: 17 mass % to 34 mass % of Zn; 0.02 mass % to2.0 mass % of Sn; 1.5 mass % to 5 mass % of Ni; 0.0005 mass % or moreand 0.2 mass % or less in total of at least one or more selected fromFe, Co, Mg, Mn, Ti, Zr, Cr, Si and rare earth metal elements, eachcontained in an amount of 0.0005 mass % or more and 0.05 mass % or less;and a balance consisting of Cu and unavoidable impurities, in which a Zncontent [Zn] (mass %), a Sn content [Sn] (mass %), and a Ni content [Ni](mass %) satisfy relationships of

12≤f1=[Zn]+5×[Sn]−2×[Ni]≤30,

10≤f2=[Zn]−0.3×[Sn]−2×[Ni]≤28, and

10≤f3={f1×(32−f1)×[Ni]}^(1/2)≤33,

the Sn content [Sn] (mass %) and the Ni content [Ni] (mass %) satisfyrelationships of

1.2≤0.7×[Ni]+[Sn]≤4, and

1.4≤[Ni]/[Sn]≤90,

conductivity is 13% IACS or more and 25% IACS or less, and in ametallographic structure, a ratio of an a phase in a constituent phaseof the metallographic structure is 99.5% or more by area ratio or anarea ratio of a γ phase (γ)% and an area ratio of a β phase (β)% of an αphase matrix satisfy a relationship of 0≤2×(γ)+(β)≤0.7, and the γ phasehaving an area ratio of 0% to 0.3% and the β phase having an area ratioof 0% to 0.5% are dispersed in the α phase matrix.

According to a sixth aspect of the present invention, there is provideda copper alloy including: 17 mass % to 34 mass % of Zn; 0.02 mass % to2.0 mass % of Sn; 1.5 mass % to 5 mass % of Ni; at least one or moreselected from 0.003 mass % to 0.09 mass % of P, 0.005 mass % to 0.5 mass% of Al, 0.01 mass % to 0.09 mass % of Sb, 0.01 mass % to 0.09 mass % ofAs, and 0.0005 mass % to 0.03 mass % of Pb; 0.0005 mass % or more and0.2 mass % or less in total of at least one or more selected from Fe,Co, Mg, Mn, Ti, Zr, Cr, Si and rare earth metal elements, each containedin an amount of 0.0005 mass % or more and 0.05 mass % or less; and abalance consisting of Cu and unavoidable impurities, in which a Zncontent [Zn] (mass %), a Sn content [Sn] (mass %), and a Ni content [Ni](mass %) satisfy relationships of

12≤f1=[Zn]+5×[Sn]−2×[Ni]≤30,

10≤f2=[Zn]−0.3×[Sn]−2×[Ni]≤28, and

10≤f3={f1×(32−f1)×[Ni]}^(1/2)≤33,

the Sn content [Sn] (mass %) and the Ni content [Ni] (mass %) satisfyrelationships of

1.2≤0.7×[Ni]+[Sn]≤4, and

1.4≤[Ni]/[Sn]≤90,

conductivity is 13% IACS or more and 25% IACS or less, and in ametallographic structure, a ratio of an a phase in a constituent phaseof the metallographic structure is 99.5% or more by area ratio or anarea ratio of a γ phase (γ)% and an area ratio of a β phase (β)% of an αphase matrix satisfy a relationship of 0≤2×(γ)+(β)≤0.7, and the γ phasehaving an area ratio of 0% to 0.3% and the β phase having an area ratioof 0% to 0.5% are dispersed in the α phase matrix.

According to a seventh aspect of the present invention, there isprovided a copper alloy including: 18 mass % to 33 mass % of Zn; 0.2mass % to 1.5 mass % of Sn; 1.5 mass % to 4 mass % of Ni; 0.003 mass %to 0.08 mass % of P; 0.0005 mass % or more and 0.2 mass % or less intotal of at least one or more selected from Fe, Co, Mg, Mn, Ti, Zr, Cr,Si and rare earth elements, each contained in an amount of 0.0005 mass %or more and 0.05 mass % or less; and a balance consisting of Cu andunavoidable impurities, in which a Zn content [Zn] (mass %), a Sncontent [Sn] (mass %), and a Ni content [Ni] (mass %) satisfyrelationships of

15≤f1=[Zn]+5×[Sn]−2×[Ni]≤30,

12≤f2=[Zn]−0.3×[Sn]−2×[Ni]≤28, and

10≤f3={f1×(32−f1)×[Ni]}^(1/2)≤30,

the Sn content [Sn] (mass %) and the Ni content [Ni] (mass %) satisfyrelationships of

1.4≤0.7×[Ni]+[Sn]≤3.6, and

1.6≤[Ni]/[Sn]≤12,

the Ni content [Ni] (mass %) and the P content [P] (mass %) satisfy arelationship of

25≤[Ni]/[P]≤750,

conductivity is 14% IACS or more and 25% IACS or less, and ametallographic structure is composed of an a single phase.

According to an eighth aspect of the present invention, there isprovided the copper alloy according to any one of the first to seventhaspects which is applicable to medical appliances, handrails, doorhandles, water supply and drain sanitary facilities, apparatuses andcontainers, and drainage tanks.

According to a ninth aspect of the present invention, there is providedthe copper alloy according to any one of the first to seventh aspectswhich is used for electronic and electrical components and automobilecomponents such as connectors, terminals, relays, and switches. It isparticularly preferable that the copper alloys according to the second,fourth and seventh aspects are applicable to electronic and electricalcomponents such as connectors, terminals, relays, and switches, andautomobile components.

According to a tenth aspect of the present invention, there is provideda copper alloy sheet including the copper alloy according to any one ofthe first to ninth aspects, in which the copper alloy sheet is producedby a production process sequentially including a hot rolling process, acold rolling process, a recrystallization heat treatment process, and afinish cold rolling process, a cold working rate in the cold rollingprocess is 40% or more, the recrystallization heat treatment processincludes a heating step of heating the cold-rolled copper alloy materialto a predetermined temperature using a continuous heat treatmentfurnace, a holding step of holding the copper alloy material at apredetermined temperature for a predetermined period of time after theheating step, and a cooling step of cooling the copper alloy material toa predetermined temperature after the holding step, and in therecrystallization heat treatment process, when a maximum reachingtemperature of the copper alloy material is denoted by Tmax (° C.), anda heating and holding time in a temperature range of a temperature 50°C. lower than the maximum reaching temperature of the copper alloymaterial to the maximum reaching temperature is denoted by tm (min),

540≤Tmax≤790,

0.04≤tm≤1.0, and

500≤It1=(Tmax−30×tm^(−1/2))≤680. Depending on the sheet thickness of thecopper alloy sheet, a pair of a cold rolling process and an annealingprocess including batch annealing may be carried out one time or pluraltimes between the hot rolling process and the cold rolling process.

According to an eleventh aspect of the present invention, there isprovided the copper alloy sheet according to the tenth aspect in whichthe production process includes a recovery heat treatment process whichis carried out after the finish cold rolling process, the recovery heattreatment process includes a heating step of heating the finishcold-rolled copper alloy material to a predetermined temperature, aholding step of holding the copper alloy material at a predeterminedtemperature for a predetermined period of time after the heating step,and a cooling step of cooling the copper alloy material to apredetermined temperature after the holding step, and when a maximumreaching temperature of the copper alloy material is denoted by Tmax2 (°C.), and a heating and holding time in a temperature range of atemperature 50° C. lower than the maximum reaching temperature of thecopper alloy material to the maximum reaching temperature is denoted bytm2 (min),

150≤Tmax≤2580,

0.02≤tm2≤100, and

120≤It2=(Tmax2−25×tm2^(−1/2))≤390.

According to a twelfth aspect of the present invention, there isprovided a method of producing a copper alloy sheet which is composed ofthe copper alloy according to any one of the first to ninth aspectsincluding: a casting process; a pair of a cold rolling process and anannealing process; a cold rolling process; a recrystallization heattreatment process; a finish cold rolling process; and a recovery heattreatment process, in which a process of hot-rolling a copper alloy or arolled material is not included, either or both of a combination of thecold rolling process and the recrystallization heat treatment processand a combination of the finish cold rolling process and the recoveryheat treatment process are carried out, a cold working rate in the coldrolling process is 40% or more, the recrystallization heat treatmentprocess includes a heating step of heating the cold-rolled copper alloymaterial to a predetermined temperature using a continuous heattreatment furnace, a holding step of holding the copper alloy materialat a predetermined temperature for a predetermined period of time afterthe heating step, and a cooling step of cooling the copper alloymaterial to a predetermined temperature after the holding step, in therecrystallization heat treatment process, when a maximum reachingtemperature of the copper alloy material is denoted by Tmax (° C.), anda heating and holding time in a temperature range of a temperature 50°C. lower than the maximum reaching temperature of the copper alloymaterial to the maximum reaching temperature is denoted by tm (min),

540≤Tmax≤790,

0.04≤tm≤1.0, and

500≤It1=(Tmax−30×tm ^(1/2))≤680,

the recovery heat treatment process includes a heating step of heatingthe finish cold-rolled copper alloy material to a predeterminedtemperature, a holding step of holding the copper alloy material at apredetermined temperature for a predetermined period of time after theheating step, and a cooling step of cooling the copper alloy material toa predetermined temperature after the holding step, and when a maximumreaching temperature of the copper alloy material is denoted by Tmax2 (°C.), and a heating and holding time in a temperature range of atemperature 50° C. lower than the maximum reaching temperature of thecopper alloy material to the maximum reaching temperature is denoted bytm2 (min),

150≤Tmax2≤580,

0.02≤tm2≤100, and

120≤It2=(Tmax2−25×tm2^(−1/2))≤390.

Advantage of the Invention

According to the present invention, it is possible to provide a copperalloy which has excellent cost performance, a small density,conductivity higher than the conductivity of phosphor bronze and nickelsilver, high strength, balance between strength and elongation andbending workability, excellent stress relaxation characteristics, stresscorrosion cracking resistance, color fastness, and antimicrobialproperties, and is adaptable to various use environments.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, copper alloys according to embodiments of the presentinvention will be described. The copper alloys according to theembodiments are used for terminals and connectors for automobiles,electronic and electric apparatuses. Further, the copper alloy isapplicable to medical appliances, public use such as handrails, doorhandles, and water supply and drain sanitary facilities, apparatuses andcontainers, public-based use, and construction-related use, and is usedas a member including a joint portion of a seam welded pipe, a weldedpipe, or the like.

Here, in the specification, a chemical symbol in parenthesis, such as[Zn], is considered to indicate the content (mass %) of thecorresponding element.

In the embodiment, plural composition relational expressions will bedefined by using the above method of indicating the content as shownbelow. Further, since the contents of the respective unavoidableimpurities of effective additive elements such as Co and Fe, andunavoidable impurities have little influence on the characteristics of acopper alloy sheet, these contents are also not considered in respectivecalculation expressions, which will be described later. For example,less than 0.005 mass % of Cr is considered as an unavoidable impurity.

Composition relational expression f1=[Zn]+5×[Sn]−2×[Ni]

Composition relational expression f2=[Zn]−0.3×[Sn]−2×[ni]

Composition relational expression f3={f1×(32−f1)×[Ni]}^(1/2)

Composition relational expression f4=0.7×[Ni]+[Sn]

Composition relational expression f5=[Ni]/[Sn]

Composition relational expression f6=[Ni]/[P]

A copper alloy according to a first embodiement of the present inventionincludes 17 mass % to 34 mass % of Zn, 0.02 mass % to 2.0 mass % of Sn,1.5 mass % to 5 mass % of Ni, and a balance consisting of Cu andunavoidable impurities, a composition relational expression f1 is withina range of 12≤f1≤30, a composition relational expression f2 is within arange of 10≤f2≤28, a composition relational expression f3 is within arange of 10≤f3≤33, a composition relational expression f4 is within arange of 1.2≤f4≤4, and a composition relational expression f5 is withina range of 1.4≤f5≤90.

A copper alloy according to a second embodiment of the present inventionincludes 18 mass % to 33 mass % of Zn, 0.2 mass % to 1.5 mass % of Sn,1.5 mass % to 4 mass % of Ni, and a balance consisting of Cu andunavoidable impurities, a composition relational expression f1 is withina range of 15≤f1≤30, a composition relational expression f2 is within arange of 12≤f2≤28, a composition relational expression f3 is within arange of 10≤f3≤30, a composition relational expression f4 is within arange of 1.4≤f4≤3.6, and a composition relational expression f5 iswithin a range of 1.6≤f5≤12.

A copper alloy according to a third embodiment of the present inventionincludes 17 mass % to 34 mass % of Zn, 0.02 mass % to 2.0 mass % of Sn,1.5 mass % to 5 mass % of Ni, at least one or more selected from 0.003mass % to 0.09 mass % of P, 0.005 mass % to 0.5 mass % of Al, 0.01 mass% to 0.09 mass % of Sb, 0.01 mass % to 0.09 mass % of As, and 0.0005mass % to 0.03 mass % of Pb, and a balance consisting of Cu andunavoidable impurities, a composition relational expression f1 is withina range of 12≤f1≤30, a composition relational expression f2 is within arange of 10≤f2≤28, a composition relational expression f3 is within arange of 10≤f3≤33, a composition relational expression f4 is within arange of 1.2≤f4≤4, and a composition relational expression f5 is withina range of 1.4≤f5≤90.

A copper alloy according to a fourth embodiment of the present inventionincludes 18 mass % to 33 mass % of Zn, 0.2 mass % to 1.5 mass % of Sn,1.5 mass % to 4 mass % of Ni, 0.003 mass % to 0.08 mass % of P, abalance consisting of Cu and unavoidable impurities, a compositionrelational expression f1 is within a range of 15≤f1≤30, a compositionrelational expression f2 is within a range of 12≤f2≤28, a compositionrelational expression f3 is within a range of 10≤f3≤30, a compositionrelational expression f4 is within a range of 1.4≤f4≤3.6, a compositionrelational expression f5 is within a range of 1.6≤f5≤12, and acomposition relational expression f6 is within a range of 25≤f6≤750.

A copper alloy according to a fifth embodiment of the present inventionincludes 17 mass % to 34 mass % of Zn, 0.02 mass % to 2.0 mass % of Sn,1.5 mass % to 5 mass % of Ni, 0.0005 mass % or more and 0.2 mass % orless in total of at least one or more selected from Fe, Co, Mg, Mn, Ti,Zr, Cr, Si and rare earth elements, each contained in an amount of0.0005 mass % or more and 0.05 mass % or less, and a balance consistingof Cu and unavoidable impurities, a composition relational expression f1is within a range of 12≤f1≤30, a composition relational expression f2 iswithin a range of 10≤f2≤28, a composition relational expression f3 iswithin a range of 10≤f3≤33, a composition relational expression f4 iswithin a range of 1.2≤f4≤4, and a composition relational expression f5is within a range of 1.4≤f5≤90.

A copper alloy according to a sixth embodiement of the present inventionincludes 17 mass % to 34 mass % of Zn, 0.02 mass % to 2.0 mass % of Sn,1.5 mass % to 5 mass % of Ni, at least one or more selected from 0.003mass % to 0.09 mass % of P, 0.005 mass % to 0.5 mass % of Al, 0.01 mass% to 0.09 mass % of Sb, 0.01 mass % to 0.09 mass % of As, and 0.0005mass % to 0.03 mass % of Pb, 0.0005 mass % or more and 0.2 mass % orless in total of at least one or more selected from Fe, Co, Mg, Mn, Ti,Zr, Cr, Si and rare earth elements, each contained in an amount of0.0005 mass % or more and 0.05 mass % or less, and a balance consistingof Cu and unavoidable impurities, a composition relational expression f1is within a range of 12≤f1≤30, a composition relational expression f2 iswithin a range of 10≤f2≤28, a composition relational expression f3 iswithin a range of 10≤f3≤33, a composition relational expression f4 iswithin a range of 1.2≤f4≤4, and a composition relational expression f5is within a range of 1.4≤f5≤90.

A copper alloy according to a seventh embodiement of the presentinvention includes 18 mass % to 33 mass % of Zn, 0.2 mass % to 1.5 mass% of Sn, 1.5 mass % to 4 mass % of Ni, 0.003 mass % to 0.08 mass % of P,0.0005 mass % or more and 0.2 mass % or less in total of at least one ormore selected from Fe, Co, Mg, Mn, Ti, Zr, Cr, Si and rare earthelements, each contained in an amount of 0.0005 mass % or more and 0.05mass % or less, and a balance consisting of Cu and unavoidableimpurities, a composition relational expression f1 is within a range of15≤f1≤30, a composition relational expression f2 is within a range of12≤f2≤28, a composition relational expression f3 is within a range of10≤f3≤30, a composition relational expression f4 is within a range of1.4≤f4≤3.6, a composition relational expression f5 is within a range of1.6≤f5≤12, and a composition relational expression f6 is within a rangeof 25≤f6≤750.

The copper alloys according to the above-described first, third, fifthand sixth embodiments of the present invention have α metallographicstructure in which the ratio of an a phase in the constituent phase ofthe metallographic structure is 99.5% or more by area ratio or an arearatio of a γ phase (γ)% and an area ratio of a β phase (β)% in an αphase matrix satisfy a relationship of 0≤2×(γ)+(β)≤0.7, and the γ phasehaving an area ratio of 0% to 0.3% and the β phase having an area ratioof 0% to 0.5% are dispersed in the α phase matrix.

In addition, the copper alloys according to the second, fourth andseventh embodiments of the present invention have a metallographicstructure composed of an a single phase.

In the copper alloys according to the above-described first, third,fifth and sixth embodiments of the present invention, the conductivityis set to be within a range of 13% IACS or more and 25% IACS or less andin copper alloys according to the second, fourth and seventh embodimentsof the present invention, the conductivity is set to be within a rangeof 14% IACS or more and 25% IACS or less.

Hereinafter, the reasons why the component composition, the compositionrelational expressions f1, f2, f3, f4, f5 and f6, the metallographicstructure, and the conductivity are defined as described above will bedescribed.

(Zn)

Zn is a main element of the alloy together with Cu and to solve theproblems of the present invention, at least 17 mass % or more of Zn isrequired. Zn is inexpensive compared to Cu, Ni and Sn. In order tofurther reduce costs, the density of the alloy of the present inventionis decreased by about 3% or more compared to pure copper and the densityof the alloy of the present invention is decreased by about 2% or morecompared to representative phosphor bronze or nickel silver. Inaddition, in order to improve strength such as tensile strength, proofstress, yield stress, spring properties, and fatigue strength, improvecolor fastness at a high temperature and high humidity, and obtain finegrains, it is required that the Zn content be 17 mass % or more. Inorder to make these effects more significant, the Zn content ispreferably 18 mass % or more or 20 mass % or more, and more preferably23 mass % or more. When the copper alloy contains a high concentrationof Zn, the cost of the raw material is reduced and the density islowered. Thus, a copper alloy having further excellent cost performanceis obtained.

On the other hand, in the case in which the Zn content is more than 34mass %, even when Ni and Sn are contained in the copper alloy within thecomposition range of the specification, which will be described later,first, it is difficult to obtain satisfactory stress relaxationcharacteristics and stress corrosion cracking resistance due todeterioration in ductility and bending workability, conductivitydeteriorates and the effect of improving strength is also saturated. TheZn content is more preferably 33 mass % or less and still morepreferably 30 mass % or less.

In the related art, it is hard to find a copper alloy containing 17 mass% or more, 18 mass % or more, or 23 mass % or more of Zn and havingexcellent stress relaxation characteristics and color fastness, andsatisfactory strength, stress corrosion cracking resistance, andconductivity.

(Ni)

The alloy of the present invention contains Ni to improve colorfastness, antimicrobial properties at a high temperature and highhumidity, stress corrosion cracking resistance, stress relaxationcharacteristics, heat resistance, and ductility and bending workability,balance among strength, ductility and bending workability. Particularly,when the Zn content is as high as 18 mass % or more, 20 mass % or more,or 23 mass % or more, the above-described characteristics moreeffectively work. In order to exhibit these effects, it is required thatthe copper alloy contain 1.5 mass % or more of Ni, preferably contain1.6 mass % or more of Ni, and satisfy the composition relationalexpressions of f1 to f6. On the other hand, when the content of Ni ismore than 5 mass %, an increase in costs is incurred and the color ofthe alloy changes from brass yellow to a pale color. The stressrelaxation characteristics begin to be saturated and antimicrobialproperties are saturated. Also, conductivity is lowered. Thus, the Nicontent is set to 5 mass % or less and preferably 4 mass % or less.Particularly, in applications such as terminals, connectors and thelike, from the viewpoint of conductivity, the Ni content is morepreferably 3 mass % or less.

(Sn)

Sn is co-added to the alloy with Ni to improve the strength of the alloyof the present invention so as to improve color fastness, stresscorrosion cracking resistance, stress relaxation characteristics,balance between strength and ductility and bending workability. Then,the grains are refined at the time of recrystallization. In order toexhibit these effects, it is required that the Sn content be at least0.02 mass % or more and particularly in order to improve color fastnessand stress relaxation characteristics, it is required that the Sncontent be 0.2 mass % or more and it is also required for the copperalloy to satisfy the composition relational expressions of f1 to f5. Inorder to make these effects more significant, the Sn content ispreferably 0.25 mass % or more and more preferably 0.3 mass % or more.On the other hand, even when the Sn content is 2 mass % or more, theeffect of stress corrosion cracking resistance and stress relaxationcharacteristics is not saturated and rather is deteriorated, whichcauses an increase in costs and a decrease in conductivity. Hotworkability, and cold ductility and bending workability aredeteriorated. When the concentration of Zn is 23 mass % or more andparticularly, is as high as 26 mass % or more, the β phase and the γphase are likely to remain substantially. The Sn content is preferably1.5 mass % or less, more preferably 1.2 mass % or less, and still morepreferably 1.0 mass % or less.

(P)

P combines with Ni to particularly improve stress relaxationcharacteristics and further lower the sensitivity for stress corrosioncracking and is effective for improving color fastness. P can reduce thesize of the grains. The copper alloys according to the fourth andseventh embodiments contain P.

Here, in order to exhibit the above-described effect, a P content of0.003 mass % or more is required. On the other hand, even when the Pcontent is more than 0.09 mass %, the above-described effect issaturated and a large amount of precipitates mainly composed of P and Niare formed and the particle size of the precipitates is also increased.Thus, bending workability is lowered. The P content is preferably 0.08mass % or less and more preferably 0.06 mass % or less. The ratiobetween Ni and P which will be described later (composition relationalexpression f6) is important.

(At Least One or More Selected from P, Al, Sb, As, and Pb)

P, Al, Sb, As, and Pb improve the color fastness, stress corrosioncracking resistance, and punchability of the alloy. The copper alloysaccording to the third and sixth embodiments contain these elements.

In order to exhibit the above-described effect, P: 0.003 mass % or more,Al: 0.005 mass % or more, Sb: 0.01 mass % or more, As: 0.01 mass % ormore, and Pb: 0.0005 mass % or more are preferable. On the other hand,even when the contents of P, Al, Sb, As, and Pb respectively exceeds P:0.09 mass %, Al: 0.5 mass %, Sb: 0.09 mass %, As: 0.09 mass %, and Pb:0.03 mass %, the effect is saturated and bending workability isdeteriorated.

(At Least One or More Selected from Fe, Co, Mg, Mn, Ti, Zr, Cr, Si andRare Earth Elements)

Elements of Fe, Co, Mg, Mn, Ti, Zr, Cr, Si and rare earth elements havethe effect of improving various characteristics. Particularly, Fe, Co,Mg, Mn, Ti, and Zr form compounds with P or Ni and the growth ofrecrystallized grains is suppressed at the time of annealing. Thus, theeffect of grain refinement is significant. The copper alloys accordingto the fifth and sixth embodiments contain these elements.

In order to exhibit the above-described effects, it is required that anyelement of Fe, Co, Mg, Mn, Ti, Zr, Cr, Si and rare earth elements beeach contained in an amount of 0.0005 mass % or more. On the other hand,when the content of the element is also more than 0.05 mass %, theeffects are not saturated and bending workability is impaired. Thecontent of the element is preferably 0.03 mass % or less. Further, whenthe total content of these elements is more than 0.2 mass %, the effectsare not saturated and bending workability is impaired. The total contentof these elements is preferably 0.15 mass % or less and more preferably0.1 mass % or less.

In addition, when an alloy contains P, Fe and Co, the effect of grainrefinement is a particularly significant. Even when the amount of Fe orCo is very small, Fe or Co easily forms a compound with P. As a result,a compound of Ni and P containing Fe or Co is formed and the particlesize of the compound is refined. In the refined compound, the size ofthe recrystallized grains at the time of annealing is made finer toimprove strength. However, when the effect is excessive, bendingworkability and stress relaxation characteristics are impaired. Mostsuitably, the content of Fe or Co is 0.001 mass % or more and 0.03 mass% or less or 0.02 mass % or less.

(Unavoidable Impurities)

In the copper alloy, elements such as oxygen, hydrogen, water vapor,carbon, and sulfur are unavoidably included in a raw material includinga returned material and the production process mainly including meltingin the atmosphere, although the amounts thereof are very small. Thus,the alloy naturally includes these unavoidable impurities.

Here, in the copper alloy according to the embodiment, elements otherthan the defined constituent elements may be considered as unavoidableimpurities. The content of the unavoidable impurities is preferably 0.1mass % or less. In addition, elements other than Zn, Ni and Sn among thedefined elements in the copper alloy according to the embodiment may becontained in the copper alloy within a range of less than the lowerlimit defined as the amount of impurities in the above.

(Composition Relational Expression f1)

The composition relational expression f1=[Zn]+5×[Sn]−2×[Ni]=30 shows aboundary value for determining whether the metallographic structure ofthe alloy of the present invention is substantially composed of only ana phase. Further, in production of a seam welded pipe, a welded pipe, orthe like, or at brazing, even when the base metal is locally melted orheated to a high temperature, the composition relational expressionshows a boundary value for obtaining a metallographic structure in whichat three sites of a joint portion or a melt zone, a heat affected zone,and the base metal, the average ratio of an α phase in the constituentphase is 99.5% or more by area ratio, or the area ratio of a γ phase(γ)% and the area ratio of a β phase (β)% in an a phase matrix satisfy arelationship of 0≤2×(γ)+(β)≤0.7 and the γ phase having an area ratio of0% to 0.3% and the β phase having an area ratio of 0% to 0.5% aredispersed in the α phase matrix.

The upper limit of the composition relational expression f1 is also aboundary value for obtaining satisfactory stress relaxationcharacteristics, color fastness, antimicrobial properties, ductility,bending workability and stress corrosion cracking resistance. When thecontent of the main element Zn is 34 mass % or less or 33 mass % orless, the relational expression has to be satisfied. For example, whenSn which is a low melting metal is contained in the Cu—Zn alloy in anamount of 0.2 mass % or 0.3 mass % or more, Sn is precipitated at afinal solidified portion and at a grain boundary at the time of casting.As a result, the concentration of Sn is increased and γ and β phases areformed. When the value of the above expression is more than 30, it isdifficult to make the γ phase and the β phase present in anon-equilibrium state disappear through casting, hot working, annealingand a heat treatment. In the same manner, when a seam welded pipe, awelded pipe, or the like is produced, the material is locally melted orheated to a high temperature in joining by brazing and the like and thusSn and the like are precipitated again.

In the composition relational expression f1, within the compositionrange of the present invention, as the coefficient of Sn, “+5” is given.This coefficient “5” is larger than the coefficient of Zn which is amain element of “1”. On the other hand, within the composition range ofthe present invention, Ni has properties of reducing Sn precipitationand suppressing the formation of the γ and β phases and has acoefficient of “−2”. When the value of the composition relationalexpression f1=[Zn]+5×[Sn]−2×[Ni] is 30 or less, the γ phase and the βphase are not present or the amounts thereof are very small even in themachining state of a product such as a seam welded pipe or the like.Thus, ductility and bending workability are satisfactory and stressrelaxation characteristics and color fastness are improved. Accordingly,bending workability of sites including the joint portion is improved.The value of the composition relational expression f1=[Zn]+5×[Sn]−2×[Ni]is more preferably 29.5 or less, and still more preferably 29 or less.On the other hand, when the value of the composition relationalexpression f1=[Zn]+5×[Sn]−2×[Ni] is less than 12, strength is loweredand color fastness is also deteriorated. Thus, the value is 12 or more,preferably 15 or more, and more preferably 20 or more. The fact that thevalue of the composition relational expression f1 is large refers to acopper alloy in a state immediately before β and γ phases areprecipitated.

(Composition Relational Expression f2)

The composition relational expression f2=[Zn]−0.3×[Sn]−2×[Ni]=28 shows aboundary value for obtaining satisfactory stress corrosion crackingresistance, ductility and bending workability. As described above, afatal defect of the Cu—Zn alloy is high sensitivity for stress corrosioncracking. In the case of the Cu—Zn alloy, sensitivity for stresscorrosion cracking is dependent on the Zn content. When the Zn contentis more than 25 mass % or 26 mass %, the sensitivity for stresscorrosion cracking is particularly increased. The composition relationalexpression f2=[Zn]−0.3×[Sn]−2×[Ni]=28 corresponds to a Zn content of theCu—Zn alloy of 25 mass % or 26 mass %. Within the composition range ofthe specification in which Ni and Sn are co-added, as shown in the aboveexpression, the coefficient of Ni is “−2” and incorporation of Ni makesit possible to particularly lower the sensitivity for stress corrosioncracking resistance. The value of the composition relational expressionf2=[Zn]−0.3×[Sn]−2×[Ni] is preferably 27 or less and more preferably 26or less. In the case of requiring high reliability in a severe stresscorrosion cracking environment, the value is or less. On the other hand,when the value of the composition relational expression f2 is less than10, strength is lowered. Thus, the value is 10 or more, preferably 12 ormore, and more preferably 15 or more.

(Composition Relational Expression f3)

In the composition relational expression f3={f1×(32−f1)×[Ni]}^(1/2),when the value of f1 is 30 or less, and the value of the compositionrelational expression f3 is 10 or more by co-addition of Ni and Sn,irrespective of containing a high concentration of Zn, excellent stressrelaxation characteristics are exhibited. The value of the compositionrelational expression f3 is preferably 12 or more and more preferably 14or more. Particularly, when the value of the composition relationalexpression f1 is in a range of up to 20, stress relaxationcharacteristics are significantly improved. On the other hand, even whenthe value of the composition relational expression f3 is more than 33,the effect is saturated and there is an influence on cost performanceand conductivity. The value of the composition relational expression f3is preferably 30 or less, more preferably 28 or less, or 25 or less.When the conditions of these preferable ranges,1.4≤f4=0.7×[Ni]+[Sn]≤3.6, 1.6≤f5=[Ni]/[Sn]≤12, incorporation of P, and25≤f6=[Ni]/[P]≤750, which will be described later, are satisfied,further excellent stress relaxation characteristics are exhibited interminals and connectors which are used in a severe high temperatureenvironment.

(Composition Relational Expression f4)

Within the composition range of the specification, in order to improvethe color fastness of the alloy, satisfy both color fastness andantimicrobial properties, and improve stress relaxation characteristics,it is required that the value of the composition relational expressionf4=0.7×[Ni]+[Sn] be 1.2 or more. The value of the composition relationalexpression f4=0.7×[Ni]+[Sn] is preferably 1.4 or more, more preferably1.6 or more, and to particularly improve color fastness, 1.8 or more isstill more preferable. On the other hand, when the value of thecomposition relational expression f4 is more than 4, the costs of thealloy increase and conductivity is also deteriorated. While the colorfastness is improved, there is a concern of lowering of antimicrobialproperties. Thus, the value is preferably 4 or less, more preferably 3.6or less, and still more preferably 3 or less. That is, the range of thecomposition relational expression f4 for obtaining particularlyexcellent color fastness, stress relaxation characteristics andconductivity is 1.4≤f4=0.7×[Ni]+[Sn]≤3.6.

(Composition Relational Expression f5)

In the stress relaxation characteristics of the Cu—Zn alloy in which Niand Sn within the composition range of the specification are co-addedand Zn is contained in a high concentration, the composition relationalexpression f5=[Ni]/[Sn] is important. When the alloy contains 1.5 mass %or more of Ni and at least two divalent Ni atoms or more are presentwith respect to one tetravalent Sn atom which is present in the matrix,that is, when the value of the mass ratio of [Ni]/[Sn] is 1 or more,stress relaxation characteristics begin to be improved. Particularly, ithas been found that when three divalent Ni atoms or more are alreadypresent with respect to one Sn atom, that is, the value of the massratio of [Ni]/[Sn] is 1.5 or more, stress relaxation characteristics arefurther improved and color fastness is also improved. The effect ofstress relaxation characteristics becomes significant in the alloy ofthe present invention that is subjected to a recovery treatment afterfinish rolling. Further, in the concentration ranges of Ni and Sndefined in the specification, when the value of [Ni]/[Sn] is less thanabout 1.4, bending workability is impaired and stress corrosion crackingresistance is also deteriorated. Accordingly, in the present invention,the value of [Ni]/[Sn] is 1.4 or more, preferably 1.6 or more, and mostpreferably 1.8 or more. On the other hand, when the upper limit of thecomposition relational expression f5=[Ni]/[Sn] is 90 or less,satisfactory stress relaxation characteristics and color fastness areexhibited. The upper limit is preferably 30 or less, more preferably 12or less, and most preferably 10 or less. When 1.6≤f5=[Ni]/[Sn]≤12, interminals and connectors used in a severe high temperature environmentsuch as an engine room of an automobile or the like, particularlyexcellent stress relaxation characteristics can be exhibited.

(Composition Relational Expression f6)

Further, stress relaxation characteristics are affected by Ni in a solidsolution state, P, and in a compound of Ni and P. When the value of thecomposition relational expression f6=[Ni]/[P] is less than 25, the ratioof a compound of Ni and P to Ni in a solid solution state is increased.Thus, stress relaxation characteristics are deteriorated and bendingworkability is also deteriorated. That is, when the value of thecomposition relational expression f6=[Ni]/[P] is 25 or more andpreferably 30 or more, stress relaxation characteristics and bendingworkability are improved. On the other hand, when the value of thecomposition relational expression f6=[Ni]/[P] is more than 750, theamount of the compound formed with Ni and P and the amount of Psolid-soluted are reduced. Thus, stress relaxation characteristics aredeteriorated. In addition, the compound of P and Ni has an action ofrefining the grains. However, the action is reduced and the strength ofthe alloy is lowered. The value of the composition relational expressionf6=[Ni]/[P] is preferably 500 or less and more preferably 300 or less.

(Metallographic Structure)

When the β phase and the γ phase are present, ductility and bendingworkability are impaired. Particularly, stress relaxationcharacteristics and color fastness, particularly, antimicrobialproperties and stress corrosion cracking resistance in a severeenvironment are deteriorated. Thus, a metallographic structure composedof an a single phase is most preferable and at least, the ratio of the aphase is 99.5% or more and more preferably 99.8% or more by area ratio.However, a metallographic structure in which at three sites of a jointportion, a heat affected zone, and a base metal in a seam welded pipe ora welded pipe, the average ratio of an a phase in the constituent phaseof the metallographic structure is 99.5% or more by area ratio, or thearea ratio of a γ phase (γ)% and the area ratio of a β phase (β)% of anα phase matrix satisfy a relationship of 0≤2×(γ)+(β)≤0.7 and the γ phasehaving an area ratio of 0% to 0.3% and the β phase having an area ratioof 0% to 0.5% are dispersed in the α phase matrix is allowable. In thepresent invention, when the metallographic structure is observed using ametallurgical microscope at a magnification of 300 times (a micrographhaving a size of 89 mm×127 mm), a β phase and a γ phase whichsignificantly affect the characteristics and are large enough to beapparently recognized as a β phase and a γ phase are set as targets.That is, in the present invention, the metallographic structuresubstantially composed of an a single phase means that when themetallographic structure is observed using a metallurgical microscope ata magnification of 300 times excluding non-metallic inclusions includingoxides, and intermetallic compounds such as precipitates andcrystallized products, the ratio of the a phase in the metallographicstructure is 100%. Similarly, when the metallographic structure isobserved using a metallurgical microscope at a magnification of 300times, at three sites of the joint portion, the heat affected zone, andthe base metal, the average ratios of the β phase and the γ phase thatare apparently recognized as a β phase and a γ phase may satisfy arelationship between the area ratio of the γ phase (γ)% and the arearatio of the β phase (β)% of the α phase matrix of 0≤2×(γ)+(β)≤0.7 and arelationship that the area ratio of the γ phase is 0% to 0.3% and thearea ratio of the β phase is 0% to 0.5% in the α phase matrix.Considering the effect of the copper alloy that can be obtained, a morepreferable metallographic structure has a state in which the ratio of anα phase is 99.7% or more by area ratio, or the area ratio of a γ phase(γ)% and the area ratio of a β phase (β)% of an α phase matrix satisfy arelationship of 0≤2×(γ)+(β)≤0.4 and a relationship that the area ratioof the γ phase is 0% to 0.2% and the area ratio of the β phase is 0% to0.3% in the α phase matrix. However, there is no limitation thereto.

(Average Grain Size)

In the copper alloy according to the embodiment, the grain size is notparticularly defined. However, it is preferable that the average grainsize is defined as follows according to the purposes.

In the copper alloy according to the embodiment, a grain having a sizeof at least about 1 μm can be obtained although the grain size differsdepending on the process. However, when the average grain size is lessthan 2 μm, stress relaxation characteristics are deteriorated. Althoughstrength is increased, ductility and bending workability aredeteriorated. Therefore, the average grain size may be 2 μm or greaterand preferably 3 μm or greater. On the other hand, when in applicationssuch as terminals, connectors and the like, the average grain size ispreferably 10 μm or less or 8 μm or less to obtain a higher strength.Additionally, in a seam welded pipe, a welded pipe, or the like used forhandrails and door handles, from the viewpoint of formability andbending workability from a sheet material to a pipe, the average grainsize may be 3 μm or greater and preferably 5 μm or greater. From theviewpoint of strength, the average grain size may be 25 μm or less andis preferably 20 μm or less.

(Precipitate)

In the copper alloy according to the embodiment, precipitates are notparticularly defined. However, in the copper alloy containing Ni and P,it is preferable to define the size and number of precipitates for thefollowing reasons.

According to the present invention, when circular or ellipticalprecipitates mainly containing Ni and P are present, the growth ofrecrystallized grains is suppressed. Thus, fine grains can be obtainedand stress relaxation characteristics can be improved. In therecrystallization formed at the time of annealing, crystals to which asignificant strain is applied by working are replaced as new crystals towhich almost no strain is applied. However, in the recrystallization,the worked grains are not instantaneously replaced with recrystallizedgrains and a long period of time or a higher temperature is required.That is, a long period of time and a higher temperature are requiredfrom when the recrystallization starts to when the recrystallizationends. Until the recrystallization ends completely, the initially formedrecrystallized grains grow and become large. However, the growth can besuppressed by the precipitates.

In the embodiment, when the average particle size of the precipitates is3 nm to 180 nm, the effect is exhibited. When the average particle sizeof the precipitates is less than 3 nm, the growth of recrystallizedgrains is suppressed. However, the amount of the precipitates isincreased and bending workability is hindered. On the other hand, whenthe average grain size of the precipitates is greater than 180 nm, thenumber of precipitates is decreased. Thus, the action of suppressing thegrowth of the precipitates is impaired and the effect for stressrelaxation characteristics is reduced.

(Conductivity)

The upper limit of the conductivity is not particularly required to begreater than 25% IACS, or 24% IACS in the member that is the target ofthe specification. A copper alloy in which stress relaxationcharacteristics, stress corrosion cracking resistance, color fastnessand strength, which are defects of brass of the related art, areimproved is most advantageous in the specification. In addition, in doorhandles, which are formed with a seam welded pipe or a welded pipe, asone of the applications of the specification, or members which aresubjected to brazing and spot welding considering the application, whenthe thermal conductivity is excessively good, that is, when theconductivity is 25% IACS or more, local heating or the like is difficultand a joining defect occurs or strength is lowered due to excessiveheating. On the other hand, in applications such as terminals,connectors, and the like, stress relaxation characteristics areemphasized rather than conductivity. Thus, the conductivity of the alloyis set to be at least higher than the conductivity of phosphor bronzeused for a terminal or a connector and is set to be 13% IACS or more andpreferably 14% IACS or more.

(Strength)

In the embodiment, particularly, regarding applications such asconnectors and terminals, on the premise that ductility and bendingworkability are satisfactory, in samples obtained by collecting testpieces in a direction which forms 0 degree with respect to a rollingdirection and in a direction which forms 90 degrees with respect to therolling direction, as strength at room temperature, the tensile strengthis at least 500 N/mm² or more, preferably 550 N/mm² or more, morepreferably 575 N/mm² or more, and still more preferably 600 N/mm² ormore. The proof stress is at least 450 N/mm² or more, preferably 500N/mm² or more, more preferably 525 N/mm² or more, and still morepreferably 550 N/mm² or more. Thus, a reduction in thickness can beachieved. Further, as preferable strength at room temperature, thetensile strength is 800 N/mm² or less and the proof stress is 750 N/mm²or less.

Particularly, in applications such as terminals and connectors, it ispreferable that both tensile strength showing fracture strength andproof stress showing deformation strength at the initial stage are high.That is, it is preferable that the ratio between proof stress andtensile strength is large and a difference between the strength in adirection orthogonal (perpendicular) to the rolling direction of thesheet and the strength in a direction parallel with the rollingdirection of the sheet is small. Here, when the tensile strength of atest piece is collected in a direction parallel with the rollingdirection is TS_(P), the proof stress is YS_(P), the tensile strength ofa test piece collected in a direction orthogonal to the rollingdirection is TS_(O) and the proof stress is YS_(O), the above-describedrelationships are expressed by the following expressions.

(1) The ratio between proof stress and tensile strength (parallel withthe rolling direction and orthogonal to the rolling direction) is 0.9 ormore and 1 or less,

0.9≤YS _(P) /TS _(P)≤1.0, and

0.9≤YS _(O) /TS _(O)≤1.0,

and preferably,

0.92≤YS _(P) /TS _(P)≤1.0, and

0.92≤YS _(O) /TS _(O)≤1.0.

(2) The ratio between the tensile strength of a test piece collected ina direction parallel with the rolling direction and the tensile strengthof a test piece collected in a direction orthogonal to the rollingdirection is 0.9 or more and 1.1 or less,

0.9≤TS _(P) /TS _(O)≤1.1, and preferably 0.92≤TS _(P) /TS _(O)≤1.07.

(3) The ratio of the proof stress of a test piece collected in adirection parallel with the rolling direction and the proof stress of atest piece collected in a direction orthogonal to the rolling directionis 0.9 or more and 1.1 or less,

0.9≤YS _(P) /YS _(O)≤1.1, and preferably 0.92≤YS _(P) /YS _(O)≤1.07.

In order to satisfy the above relationships, the final cold working rateand an average grain size are important. When the final cold workingrate is less than 5%, high strength cannot be obtained and the ratiobetween proof stress and tensile strength is small. Preferably, the coldworking rate is 10% or more. On the other hand, when the working rate ismore than 50%, bending workability and ductility are deteriorated. Thecold working rate is preferably 35% or less. By a recovery heattreatment which will be described later, the ratio between proof stressand tensile strength can be increased and the difference between proofstress in a direction parallel with the rolling direction and proofstress in a direction perpendicular to the rolling direction can bedecreased.

When joining by local high heat or the like is carried out, for example,regarding the strength of a seam welded pipe, the tensile strength is425 N/mm² or more and preferably 475 N/mm² or more, and the proof stressis 275 N/mm² or more and preferably 325 N/mm² or more. As long as theabove-described strength is provided, in application such as handrailsor the like, a reduction in thickness can be achieved.

(Stress Relaxation Characteristics)

The copper alloy is used for terminals, connectors, and relays in anenvironment of about 100° C. or 100° C. or higher, for example, in acabin or in an environment close to an engine room of a car under theblazing sun. One main function that is required for terminals andconnectors is having high contact pressure. At room temperature, themaximum contact pressure is the stress of the elastic limit when atensile test is carried out on the material, or 80% of the proof stress.However, when the material is used for a long period of time in anenvironment of 100° C. or higher, the material is permanently deformed.Thus, the material cannot be used at the stress of elastic limit or thestress corresponding to 80% of the proof stress, and the contactpressure. A stress relaxation test is a test in which in a state inwhich 80% of proof stress is applied to the material, the material isheld at 120° C. or 150° C. for 1,000 hours and then the degree of stressrelaxation is investigated. That is, the maximum effective contactpressure when the material is used in an environment of about 100° C. or100° C. or higher is expressed by proof stress×80%×(100%−stressrelaxation rate (%)), and it is desired that not only is the proofstress at room temperature simply high but also the value of theexpression is high. In the specification, in spite of a slightly lowconductivity, particularly, excellent stress relaxation characteristicswhich a brass copper alloy of the related art does not have areemphasized. Thus, when the value of proof stress×80%×(100%−stressrelaxation rate (%)) in the test at 150° C. for 1,000 hours is 275 N/mm²or more, the copper alloy can be used at a high temperature state. Whenthe value is 300 N/mm² or more, the copper alloy is suitably used in ahigh temperature state, and when the value is 325 N/mm² or more, thecopper alloy is most suitably used. For example, in the case of 70 mass% Cu-30 mass % Zn which is a representative alloy of brass copper havinga proof stress of 500 N/mm², the value of proof stress×80%×(100%−stressrelaxation rate (%)) is about 70 N/mm² at 150° C. and in the case ofphosphor bronze of 92 mass % Cu-8 mass % Sn having a proof stress of 550N/mm², the value is about 190 N/mm². With current alloys used,satisfactory values cannot be obtained.

When the strength of the material is set to the above-described targetstrength and a stress relaxation rate in the test under the severeconditions of 150° C. and 1,000 hours is 20% or less, the copper alloyhas excellent stress relaxation characteristics at a very high levelamong copper alloys. When the stress relaxation rate is more than 20%and 25% or less, stress relaxation characteristics are excellent andwhen the stress relaxation rate is more than 25% and 35% or less, stressrelaxation characteristics are satisfactory. When the stress relaxationrate is more than 35% and 50% or less, there is a problem in use andwhen the stress relaxation rate is more than 50%, it is difficult tosubstantially use the copper alloy in a severe thermal environment. Onthe other hand, in a test under slightly mild conditions of 120° C. and1,000 hours, higher performance is required. When the stress relaxationrate is 10% or less, the level of stress relaxation characteristics ishigh. When the stress relaxation rate is more than 10% and 15% or less,stress relaxation characteristics are satisfactory and when the stressrelaxation rate is more than 15% and 30% or less, there is a problem inuse. When the stress relaxation rate is more than 30%, there is littlesuperiority as a material.

Next, a method of producing copper alloys according to first to seventhembodiments of the present invention will be described.

First, an ingot having the above-described component composition isprepared and hot working is carried out on this ingot. In order to puteach element into a solid solution state and further reduceprecipitation of Sn, or from the viewpoint of hot ductility, atemperature at which hot rolling, which is representative hot working,starts is 760° C. or higher and 890° C. or lower. It is desirable thatthe hot rolling working rate is at least 50% or more to destroy thecoarse cast structure of the ingot and reduce precipitation of anelement such as Sn. In the case in which P is contained in the copperalloy, in order to put P and Ni into a further solid solution state, thetemperature when the final rolling ends or a temperature in a range from650° C. to 350° C. is preferably cooled at an average cooling rate of 1°C./second or more so that a precipitate of P and Ni, that is, a compoundof Ni and P is not coarsened.

Then, the thickness is reduced by cold rolling and the process proceedsto recrystallization heat treatment, that is, an annealing process.Although the cold rolling reduction differs depending on the thicknessof a final product it is at least 40% or more, preferably 55% or more,and more preferably 97% or less. In order to destroy the hot rollingstructure, the cold rolling reduction is desirably 55% or more andbefore the material strain is deteriorated by strong working at roomtemperature, the rolling is ended. The grain size differs depending onthe final target grain size but, in the annealing process, the grainsize is preferably 3 μm to 40 μm. Specifically, regarding conditions oftemperature and time, in the case of batch type annealing, the annealingunder the conditions of heating from 450° C. to 650° C. and holding for1 hour to 10 hours is carried out. Alternatively, an annealing methodcalled continuous annealing that is carried out at a high temperaturefor a short period of time is used in many cases. However, in the caseof the continuous annealing, the maximum reaching temperature of thematerial is 540° C. to 790° C. and preferably 560° C. to 790° C. In ahigh temperature state of “maximum reaching temperature-50° C”, thecopper alloy is held for 0.04 minutes to 1.0 minute and preferably for0.06 minutes to 1.0 minute. The continuous annealing method is also usedin the recovery heat treatment which will be described later. Theannealing process and the cold rolling process, that is, a pair of acold rolling process and an annealing process may be omitted dependingon the thickness of a final product, the strain state of the rolledmaterial, or the like.

Next, cold rolling is carried out before finishing. The cold rollingreduction differs depending on the thickness of a final product but thecold rolling reduction is desirably 40% to 96%. In the following finalrecrystallization heat treatment, that is, final annealing, in order toobtain finer and uniform grains, it is required that the working rate be40% or more. The working rate is 96% or less in terms of the strain ofthe material and preferably 90% or less.

The final annealing is distinguished from the above-described annealingprocess and is a heat treatment to obtain a target grain size. Inapplications such as terminals, connectors and the like, the targetaverage grain size is 2 μm to 10 μm. However, when the strength isemphasized, the average grain size is preferably 2 μm to 6 μm. When thestress relaxation characteristics are emphasized, the average grain sizeis preferably 3 μm to 10 μm. The annealing conditions differ dependingon the rolling reduction before finishing, the thickness of thematerial, and the target grain size, but in the case of batch typeannealing, as preferable annealing conditions, the temperature is 350°C. to 570° C. and the holding time is 1 hour to 10 hours. In hightemperature short time annealing, the maximum reaching temperature is540° C. to 790° C. and the holding time at a temperature of the maximumreaching temperature-50° C. is 0.04 minutes to 1.0 minute. When thetemperature is in a range from 350° C. to 600° C. or the maximumreaching temperature is lower than 600° C., cooling is carried out in atemperature range to the maximum reaching temperature at an averagecooling rate of 2° C./second or higher and preferably at an averagecooling rate of 5° C./second or higher. In applications such ashandrails, medical appliances, sanitary apparatuses, construction, orthe like, in addition to strength, workability and material strain areimportant. The target average grain size is 3 μm to 25 μm. The annealingconditions differ depending on the rolling reduction before finishing,the thickness of the material, and the target grain size, but in thecase of batch-type annealing, as the annealing conditions, thetemperature is 400° C. to 630° C., and the holding time is 1 hour to 10hours. In high temperature short time annealing, the maximum reachingtemperature is 540° C. to 790° C. and the holding time at a temperatureof the maximum reaching temperature-50° C. is 0.04 minutes to 1.0minute. Preferably, the temperature is 560° C. to 790° C. and theholding time at a temperature of the maximum reaching temperature-50° C.is 0.06 minutes to 1.0 minute. When the temperature is in a range from350° C. to 600° C. or the maximum reaching temperature is lower than600° C., cooling is carried out in a temperature range to the maximumreaching temperature at an average cooling rate of 2° C./second orhigher and preferably at an average cooling rate of 5° C./second orhigher.

When the average grain size is greater than 5 μm or when stressrelaxation characteristics is improved by incorporation of P, hightemperature short time annealing is more preferable than batch-typeannealing. In the case in which the copper alloy contains the amounts ofNi and Sn defined in the specification and batch-type annealing iscarried out, when the grain size is set to be greater than 5 μm, a mixedgrain state in which large recrystallized grains and smallrecrystallized grains are mixed easily occurs. Particularly, when thecopper alloy contains P, as the temperature increases, the compound ofNi and P begins to be solid-soluted and the compound partiallydisappears. Thus, some of the recrystallized grains abnormally grow anda mixed grain state in which the recrystallized grains are mixed withfine recrystallized grains easily occurs. On the other hand, since thetemperature increases in a short period of time in the high temperatureshort time annealing, recrystallization nuclei are uniformly generatedand the time for the abnormal growth of recrystallized grains is notprovided. Therefore, a mixed grain state can be avoided. Even when thecompound of Ni and P is present, due to a rapid increase in temperature,Ni and P are almost uniformly solid-soluted, that is, the compoundalmost uniformly disappears and thus the effect of suppressing thegrowth of grains is uniformly impaired. Therefore, a mixed grain statedoes not occur and the copper alloy is composed of recrystallized grainshaving an almost uniform grain size. In addition, when the copper alloycontains P, with batch-type annealing, slow cooling is carried out.Thus, the compound of Ni and P is excessively precipitated and thebalance between Ni and P to be solid-soluted is deteriorated. Therefore,stress relaxation characteristics are slightly deteriorated. With hightemperature short time annealing, cooling is carried out in thetemperature range of 350° C. to 600° C. at an average cooling rate of 2°C./second or higher and thus the compound of Ni and P is not excessivelyprecipitated.

Specifically, the high temperature short time annealing includes aheating step of heating a copper alloy material to a predeterminedtemperature, a holding step of holding the copper alloy material at apredetermined temperature for a predetermined period of time after theheating step, and a cooling step of cooling the copper alloy material toa predetermined temperature after the holding step. When the maximumreaching temperature of the copper alloy material is denoted by Tmax (°C.), and a heating and holding time in a temperature range from atemperature 50° C. lower than the maximum reaching temperature of thecopper alloy material to the maximum reaching temperature is denoted bytm (min), 540≤Tmax≤790, and 0.04≤tm≤1.0,500≤It1=(Tmax−30×tm^(−1/2))≤700.

Particularly, in applications such as terminals, connectors, and thelike, it is preferable that 540≤Tmax≤790, 0.04≤tm≤1.0, and500≤It1=(Tmax−30×tm^(−1/2))≤680. When the maximum reaching temperatureis more than 790° C., or when Itl is more than 680, particularly 700,the size of the grains is increased, a large amount of precipitates ofNi and P is solid-soluted, and the amount of precipitates is excessivelysmall. On the other hand, since few precipitates are coarsened, the βphase or the γ phase is precipitated during a heat treatment. Therefore,stress relaxation characteristics are deteriorated, strength is lowered,and bending workability is deteriorated. In addition, there is a concernof anisotropy of mechanical properties such as tensile strength in adirection parallel with the rolling direction and a directionperpendicular to the rolling direction, proof stress, and elongationbeing generated. Preferably, Tmax is 780° C. or lower and Itl is 670 orless. On the other hand, when Tmax is lower than 540° or It1 is lessthan 500, the grains are not recrystallized and even when the grains arerecrystallized, ultrafine grains are obtained. The size thereof is lessthan 2 μm and bending workability and stress relaxation characteristicsare deteriorated. Preferably, Tmax is 550° C. or higher and Itl is 520or more. However, in a high temperature short time continuous heattreatment method, due to the structure of the apparatus, heating andcooling steps are different and the conditions are slightly deviated.However, within the above range, there is no problem.

After the final annealing, finish rolling is carried out. Although thefinish rolling reduction differs depending on the grain size, the targetstrength and bending workability, due to good balance between bendingworkability and strength, which is a target of the specification, inapplications such as terminals, connectors and the like, the finishrolling reduction is desirably 5% to 50%. At a finish rolling reductionof less than 5%, even when the grain size is as fine as 2 μm to 3 μm, itis difficult to obtain high strength, particularly, high proof stress.Thus, the rolling reduction is preferably 10% or more. On the otherhand, as the rolling reduction increases, strength is increased by workhardening. However, ductility and bending workability are deteriorated.When the size of the grains is large, at a rolling reduction more thanthan 50%, ductility and bending workability are deteriorated. Therolling reduction is preferably 40% or less and more preferably 35% orless.

After the final finish rolling, in order to improve the strain state,correction using a tension leveler is carried out. Further, inapplications such as terminals, connectors, and the like, a recoveryheat treatment without being accompanied with recrystallization in whichthe maximum reaching temperature of the rolled material is 150° C. to580° C. and a holding time at a temperature of maximum reachingtemperature-50° C. is 0.02 minutes to 100 minutes is carried out.Through this low temperature heat treatment, stress relaxationcharacteristics, an elastic limit, conductivity, mechanical properties,ductility, and a spring deflection limit are improved. After the finishrolling, when the copper alloy is formed into a sheet material or aproduct and then molten Sn plating to which thermal conditionscorresponding to the above-described conditions are applied, or a reflowSn plating process is carried out, the recovery heat treatment can beomitted.

Specifically, the recovery heat treatment process is carried out by ahigh temperature short time continuous heat treatment. The recovery heattreatment includes a heating step of heating a copper alloy material toa predetermined temperature, a holding step of holding the copper alloymaterial at a predetermined temperature for a predetermined period oftime after the heating step, and a cooling step of cooling the copperalloy material to a predetermined temperature after the holding step.When the maximum reaching temperature of the copper alloy material isdenoted by Tmax2 (° C.), and a heating and holding time at a temperaturerange from a temperature 50° C. lower than the maximum reachingtemperature of the copper alloy to the maximum reaching temperature isdenoted by tm2 (min), 150≤Tmax2≤580, 0.02≤tm2≤100, and120≤It2=(Tmax2−25×tm2^(−1/2))≤390. When Tmax2 is more than 580° C. orIt2 is more than 390, softening proceeds and partial recrystallizationis generated in some cases, which causes lowering of strength.Preferably, Tmax2 is 550° C. or lower or It2 is 380 or less. When Tmax2is lower than 150° C. or It2 is less than 120, the degree of improvementof stress relaxation characteristics is small. Most preferably, Tmax2 is250° C. or higher or It2 is 240 or more. However, in the hightemperature short time continuous heat treatment method, due to thestructure of the apparatus, heating and cooling steps are different andthe conditions are slightly deviated. However, within the above range,there is no problem.

The copper alloy according to the embodiment can be obtained byrepeatedly carrying out cold rolling and annealing on an ingot withouthot rolling and carrying out a recovery heat treatment. Specifically,through continuous casting, a thin sheet-like casting having a thicknessof 10 mm to 25 mm is prepared and as necessary, homogenization annealingat 650° C. to 850° C. for 1 hour to 24 hours is carried out. Then, apair of cold rolling and annealing is carried out one time or pluraltimes to destroy the metallographic structure of the casting and obtaina recrystallized grain structure. Thereafter, the same rolling beforefinishing, final annealing, final finish rolling, and theabove-described recovery heat treatment are carried out so that a sheetmaterial having almost the same properties as those of a materialprepared in hot rolling can be obtained. In the specification, workingthat is carried out at a temperature lower than the recrystallizationtemperature of the copper alloy material to be worked is defined as coldworking, working that is carried out at a temperature higher than therecrystallization temperature is defined as hot working, and formingworking using rolls in these processes is each defined as cold rollingand hot rolling. In addition, recrystallization is defined as a changefrom one crystal structure to another crystal structure or formation ofa new crystal structure in which no strain is present from a structurein which strain generated by working is present.

Particularly, in applications such as terminals, connectors, relays andthe like, after the final finish rolling, by substantially holding thetemperature of the rolled material at 150° C. to 580° C. for 0.02minutes to 100 minutes, stress relaxation characteristics are improved.After the finish rolling, when the copper alloy material is formed intoa sheet-like material or a product and then a Sn plating process towhich thermal conditions corresponding to the above-described conditionsare applied is to be carried out, a recovery heat treatment can beomitted. In a Sn plating process such as molten Sn plating or reflow Snplating, the copper alloy material is formed into a rolled material or aterminal or a connector in some cases at about 150° C. to 300° C. for ashort period of time and then heated. Even when the Sn plating processis carried out after the recovery heat treatment, there is littleinfluence on the characteristics of the alloy after the recovery heattreatment. On the other hand, the heating process of the Sn platingprocess is a process that is carried out instead of the recovery heattreatment process.

The recovery heat treatment is a heat treatment for improving theelastic limit, stress relaxation characteristics, spring deflectionlimit, and elongation of the material by a recovery heat treatment atlow temperature or for a short time without being accompanied withrecrystallization, and for recovering conductivity lowered due to coldrolling.

On the other hand, in the case of a general Cu—Zn alloy containing 17mass % or more of Zn, when a rolled material subjected to cold workingat a working rate of 10% or more is annealed at a low temperature, thematerial is hardened due to low temperature annealing hardening andbecomes brittle. When a recovery heat treatment is carried out under thecondition of a holding time of 10 minutes, the material is hardened at150° C. to 200° C. and the material is rapidly hardened or partiallyrecrystallized at about 250° C. and recrystallized at about 300° C. Thestrength of the rolled material is lowered to a proof stress which isabout 50% to 65% of the original proof stress of the rolled material. Inthis manner, in a narrow temperature range, mechanical properties arechanged.

Due to the effects of Ni, Sn and the like contained in the copper alloyaccording to the embodiment, after the final finish rolling, when thealloy is held, for example, at about 200° C. for 10 minutes, thestrength is slightly increased due to low temperature annealinghardening. However, when the alloy is held at about 300° C. for 10minutes, the strength has already returned to the original strength ofthe rolled material and ductility is improved. Here, when the degree oflow temperature annealing hardening is large, similar to the Cu—Znalloy, the material becomes brittle. In order to avoid theabove-described circumstance, the finish rolling reduction may be 50% orless, preferably 40% or less and more preferably 35% or less. In orderto obtain a higher strength, the rolling reduction is at least 5% ormore and preferably 10% or more. The grain size may be 2 μm or more andmore preferably 3 μm or more. In order to obtain high strength and goodbalance between strength and ductility, the grain size is 10 μm or lessand preferably 8 μm or less.

Further, in a rolled state, proof stress in a direction perpendicular tothe rolling direction is low. However, by the recovery heat treatment,ductility is rather improved without deterioration and proof stress in adirection perpendicular to the rolling direction can be improved. Due tothis effect, a difference between tensile strength and proof stress in adirection perpendicular to the rolling direction, which was about 10%,is reduced to less than 10% and a difference between tensile strengthand proof stress in a direction parallel with the rolling direction,which was about 10%, is also reduced to less than 10%. Thus, a materialhaving small anisotropy is obtained.

As described above, in the copper alloys according to the first to sixthembodiments of the present invention, excellent color fastness, highstrength, good bending workability, excellent stress relaxationcharacteristics, and satisfactory stress corrosion cracking resistanceare obtained. Due to these characteristics, the copper alloy is amaterial suitable for electronic and electrical apparatus components andautomobile components such as connectors, terminals, relays, switches,springs, and sockets, decoration and consturction tools and members suchas handrails, door handles, elevator panel materials, water supply anddrain sanitary facilities and apparatuses, and medical appliances whichhave excellent cost performance such as cheap metal costs and a lowalloy density. In addition, since the color fastness is satisfactory,plating can be omitted in some applications such as terminals andconnectors, decoration and construction members, and sanitaryfacilities. Further, in applications such as decoration and constructiontools and members such as handrails, door handles, elevator inner wallmaterials, water supply and drain sanitary facilities and apparatuses,and medical appliances, the antimicrobial effect of copper can bemaximized.

Further, when the average grain size is 2 μm to 10 μm, the conductivityis 14% IACS or more and 25% IACS or less, circular or ellipticalprecipitates are present, and the average particle size of theprecipitates is 3 nm to 180 nm, further excellent strength, excellentbalance between strength and bending workability, and high stressrelaxation characteristics, particularly, high effective stress at 150°C. can be obtained. Therefore, a material suitable for electronic andelectrical apparatus components and automobile components such asconnectors, terminals, relays, switches, springs, and sockets, which areused in a severe environment, is obtained.

Hereinabove, the embodiments of the present invention have beendescribed. However, the present invention is not limited to theseembodiement and may be appropriately modified within a scope notdeparting from the technical idea of the invention.

EXAMPLES

Hereinafter, the results of confirmation tests that were carried out toconfirm the effects of the present invention will be shown. Thefollowing examples are shown to describe the effects of the presentinvention and configurations, processes, and conditions described in theexamples do not limit the technical scope of the present invention.

Samples were prepared by using the above-described copper alloysaccording to the first to sixth embodiments of the present invention andcopper alloys having configurations for comparison and changingproduction processes. The compositions of the copper alloys are shown inTables 1 to 4. In addition, production processes are shown in Table 5.In Tables 1 to 4, composition relational expressions f1, f2, f3, f4, f5and f6 shown in the above-described embodiement are shown.

TABLE 1 Component composition (mass %) Alloy Other Compositionrelational expression No. Zn Ni Sn P elements Cu f1 f2 f3 f4 f5 f6 127.2 2.9 0.52 — — — Balance 24.0 21.2 24 2.6 5.6 — 2 23.7 3.8 1.00 — — —Balance 21.1 15.8 30 3.7 3.8 — 3 30.3 3.4 0.64 0.02 — — Balance 26.723.3 22 3.0 5.3 170  4 25.9 2.3 0.55 0.04 — — Balance 24.1 21.1 21 2.24.2 58 5 19.9 1.8 0.80 0.01 — — Balance 20.3 16.1 21 2.1 2.3 180  6 27.82.7 0.44 0.02 As — Balance 24.6 22.3 22 2.3 6.1 135  0.03 7 28.7 3.40.51 — Sb — Balance 24.5 21.7 25 2.9 6.7 — 0.04 8 30.8 2.4 0.68 0.02 — —Balance 29.4 25.8 14 2.4 3.5 120  11 32.7 2.6 0.34 — — — Balance 29.227.4 15 2.2 7.6 — 12 30.3 1.8 0.56 0.02 — — Balance 29.5 26.5 12 1.8 3.290 13 26.2 1.7 1.10 0.02 — — Balance 28.3 22.5 13 2.3 1.5 85 14 31.2 2.40.39 0.04 — — Balance 28.4 26.3 16 2.1 6.2 60 15 30.6 2.5 0.56 — — —Balance 28.4 25.4 16 2.3 4.5 — 16 27.5 1.9 0.42 0.05 — — Balance 25.823.6 17 1.8 4.5 38 17 27.6 3.5 0.75 — — — Balance 24.4 20.4 26 3.2 4.7 —18 25.8 2.0 0.46  0.005 — — Balance 24.1 21.7 20 1.9 4.3 400  19 26.23.1 0.68 — — — Balance 23.4 19.8 25 2.9 4.6 — 20 26.2 1.6 0.17 0.02 — —Balance 23.9 22.9 18 1.3 9.4 80 21 20.6 4.0 1.00 — — — Balance 17.6 12.332 3.8 4.0 — 22 21.8 3.2 0.60 0.06 — — Balance 18.4 15.2 28 2.8 5.3 53

TABLE 2 Component composition (mass %) Alloy Other Compositionrelational expression No. Zn Ni Sn P elements Cu f1 f2 f3 f4 f5 f6 2321.5 2.7 0.56 — — — Balance 18.9 15.9 26 2.5 4.8 — 24 22.2 1.9 0.45 — —— Balance 20.7 18.3 21 1.8 4.2 — 25 24.4 3.5 1.20 — — — Balance 23.417.0 27 3.7 2.9 — 26 18.5 3.0 0.95 — — — Balance 17.3 12.2 28 3.1 3.2 —27 25.8 2.5 0.71 0.03 Sb — Balance 24.4 20.6 22 2.5 3.5  83 0.04 28 27.02.2 0.48 0.02 Fe — Balance 25.0 22.5 20 2.0 4.6 110 0.0009 29 28.2 2.60.46  0.008 Fe — Balance 25.3 22.9 21 2.3 5.7 325 0.009 30 26.5 2.4 0.560.02 Co — Balance 24.5 21.5 21 2.2 4.3 120 0.003 31 27.5 3.0 0.55 — Fe —Balance 24.3 21.3 24 2.7 5.5 — 0.02 32 29.0 3.4 0.47 — Al — Balance 24.622.1 25 2.9 7.2 — 0.04 33 30.6 3.4 0.58  0.007 Mg — Balance 26.7 23.6 223.0 5.9 486 0.02 34 27.5 2.5 0.42 0.02 Mn — Balance 24.6 22.4 21 2.2 6.0125 0.02 35 26.8 3.1 0.48 — Ti Cr Balance 23.0 20.5 25 2.7 6.5 — 0.0050.005 36 27.5 2.2 0.41 0.05 Zr — Balance 25.2 23.0 19 2.0 5.4  44 0.00837 29.0 3.3 0.46 — Si — Balance 24.7 22.3 24 2.8 7.2 — 0.03 38 28.7 3.40.70  0.008 Sb — Balance 25.4 21.7 24 3.1 4.9 425 0.04 39 27.5 3.1 0.60— Sb As Balance 24.3 21.1 24 2.8 5.2 — 0.02 0.02 40 28.4 2.6 0.37 0.02Pb — Balance 25.1 23.1 21 2.2 7.0 130 0.007 41 24.4 3.9 1.00 — As —Balance 21.6 16.3 30 3.7 3.9 — 0.03 42 28.5 3.4 0.49 — Ce — Balance 24.221.6 25 2.9 6.9 — 0.01 43 24.2 2.3 0.04 0.03 — — Balance 19.8 19.6 241.7 57.5  77 44 25.4 1.9 1.00 0.07 — — Balance 26.6 21.3 17 2.3 1.9  2745 26.1 3.0 0.65  0.005 — — Balance 23.4 19.9 25 2.8 4.6 600

TABLE 3 Component composition (mass %) Alloy Other Compositionrelational expression No. Zn Ni Sn P elements Cu f1 f2 f3 f4 f5 f6 10130.7 2.3 0.91 — — — Balance 30.7 25.8 10 2.5 2.5 — 102 29.9 1.6 0.750.02 — — Balance 30.5 26.5 9 1.9 2.1 80 103 30.1 1.2 0.42 0.02 — —Balance 29.8 27.6 9 1.3 2.9 60 104 27.4 0.86 0.52 0.02 — — Balance 28.325.5 10 1.1 1.7 43 105 34.5 3.8 0.56 0.03 — — Balance 29.7 26.7 16 3.26.8 127  106 34.6 4.3 0.75 — — — Balance 29.8 25.8 17 3.8 5.7 — 107 22.92.5 2.00 — — — Balance 27.9 17.3 17 3.8 1.3 — 108 29.4 1.6 0.45 0.12 — —Balance 28.5 26.1 13 1.6 3.6 13 109 29.1 1.6 0.97 0.02 — — Balance 30.825.6 8 2.1 1.6 80 110 31.9 2.3 0.64 — — — Balance 30.5 27.1 10 2.3 3.6 —111 26.9 1.5 0.09 — — — Balance 24.4 23.9 17 1.1 16.7 — 112 31.8 1.60.22 0.04 — — Balance 29.7 28.5 10 1.3 7.3 40 113 32.5 3.4 1.00 — — —Balance 30.7 25.4 12 3.4 3.4 — 114 24.2 1.7 1.40 — — — Balance 27.8 20.414 2.6 1.2 — 115 32.0 1.8 0.30 — — — Balance 29.9 28.3 11 1.6 6.0 — 11633.2 2.9 0.71 0.05 — — Balance 31.0 27.2 10 2.7 4.1 58 117 31.9 2.2 0.78— — — Balance 31.4 27.3 6 2.3 2.8 — 118 28.1 1.7 1.20 — — — Balance 30.724.3 8 2.4 1.4 — 119 16.1 2.0 0.36 — — — Balance 13.9 12.0 22 1.8 5.6 —120 27.2 2.3 0.69 0.03 Fe — Balance 26.1 22.4 19 2.3 3.3 77 0.07 12127.9 2.6 0.63 0.02 Co — Balance 25.9 22.5 20 2.5 4.1 130  0.08 122 28.91.3 0.58 — — — Balance 29.2 26.1 10 1.5 2.2 — 123 23.3 2.1 0.02 — — —Balance 19.2 19.1 23 1.5 105.0 — 124 23.8 2.0 0.01 0.03 — — Balance 19.919.8 22 1.4 200.0 67 125 17.3 3.4 0.05 — — — Balance 10.8 10.5 28 2.468.0 — 126 25.1 1.7 1.00 0.08 — — Balance 26.7 21.4 16 2.2 1.7 21

TABLE 4 Component composition (mass %) Alloy Other Compositionrelational expression No. Zn Ni Sn P elements Cu f1 f2 f3 f4 f5 f6 20128.7 — — — — — Balance — — — — — — 202 25.5 — — — — — Balance — — — — —— 203 20.8 — — — — — Balance — — — — — — 204 17.2 — — — — — Balance — —— — — — 205 — — 7.80 0.08 — — Balance — — — — — —

TABLE 5 Hot rolling + Rolling Final milling Rolling Annealing RollingAnnealing thickness annealing Process thickness thickness TemperatureTime thickness Temperature Time before finish Temperature No. (mm) (mm)(° C.) (min) (mm) (° C.) (min) (mm) (° C.) A1-1 12 2.5 580 240 0.9 500240 0.36 425 A1-2 12 2.5 580 240 0.9 500 240 0.36 425 A1-3 12 2.5 580240 0.9 500 240 0.36 425 A1-4 12 2.5 580 240 0.9 500 240 0.36 690 A2-112 — — — 1.0 510 240 0.36 425 A2-2 12 — — — 1.0 510 240 0.36 670 A2-3 12— — — 1.0 510 240 0.36 670 A2-4 12 — — — 1.0 510 240 0.36 670 A2-5 12 —— — 1.0 510 240 0.40 690 A2-6 12 — — — 1.0 510 240 0.40 690 A2-7 12 — —— 1.0 670 0.24 0.40 705 A2-8 12 — — — 1.0 670 0.24 0.40 770 A2-9 12 — —— 1.0 510 240 0.40 580  A2-10 12 — — — 1.0 670 0.24 0.36 620 A3-1 12 — —— 1.0 680 0.3 Seam welding pipe with φ 25.4 mm prepared after being slithaving width of 86 mm B1-1 6 — — — 0.9 510 240 0.36 425 B1-2 6 — — — 0.9510 240 0.36 670 B1-3 6 — — — 0.9 510 240 0.36 670 B2-1 6 — — — — — —0.36 425 B3-1 (Annealing) 6 620 240 0.9 510 240 0.36 425 B3-2(Annealing) 6 620 240 0.9 510 240 0.36 670 C1 6 — — — 0.9 510 240 0.36425   C1A 6 — — — 0.9 510 240 0.36 670 C2 6 — — — 1.0 430 240 0.40 380Final annealing Finish rolling Recovery heat treatment Process TimeThickness Re Temperature Time No. (min) It1 (mm) (%) (° C.) (min) It2A1-1 240 — 0.3 17 300 30 295 A1-2 240 — 0.3 17 450 0.05 338 A1-3 240 —0.3 17 300 0.07 206 A1-4 0.14 610 0.3 17 450 0.05 338 A2-1 240 — 0.3 17450 0.05 338 A2-2 0.09 570 0.3 17 450 0.05 338 A2-3 0.09 570 0.3 17 3000.07 206 A2-4 0.09 570 0.3 17 — — — A2-5 0.14 610 0.3 25 450 0.05 338A2-6 0.14 610 0.3 25 250 0.15 185 A2-7 0.18 634 0.3 25 450 0.05 338 A2-80.25 710 0.3 25 450 0.05 338 A2-9 240 — 0.3 25 450 0.05 338  A2-10 0.05486 0.3 17 450 0.05 338 A3-1 Seam welding pipe with φ 25.4 mm preparedafter being slit having width of 86 mm B1-1 240 — 0.3 17 450 0.05 338B1-2 0.09 570 0.3 17 300 0.07 206 B1-3 0.09 570 0.3 17 300 30 295 B2-1240 — 0.3 17 300 30 295 B3-1 240 — 0.3 17 300 30 295 B3-2 0.09 570 0.317 300 30 295 C1 240 — 0.3 17 300 30 295   C1A 0.09 570 0.3 17 300 30295 C2 240 — 0.3 25 230 30 —

In a production process A (A1-1 to A1-4, A2-1 to A2-10, and A3-1), rawmaterials were melted in an induction melting furnace having an internalvolume of 5 tons and ingots having a cross section with a thickness of190 mm and a width of 630 mm were produced by semi-continuous casting.The ingots each were cut to have a length of 1.5 m and then a hotrolling process (sheet thickness: 13 mm)—a cooling process—a millingprocess (sheet thickness: 12 mm)—a cold rolling process were carriedout.

The hot rolling start temperature in the hot rolling process was set to820° C., the material was hot-rolled to a sheet thickness of 13 mm, andthen cooled by shower water cooling in the cooling process. The averagecooling rate in the cooling process was set to a cooling rate in atemperature range from when the temperature of the rolled material afterfinal hot rolling, or the temperature of the rolled material reached650° C. when the temperature reached 350° C. and was measured in therear end of the rolled sheet. The measured average cooling rate was 3°C./sec.

In the processes A1-1 to A1-4, a cold rolling (sheet thickness: 2.5mm)—an annealing process (580° C., holding time: 4 hours)—cold rolling(sheet thickness: 0.9 mm)—an annealing process (500° C., holding time: 4hours)—a rolling process before finishing (sheet thickness: 0.36 mm anda cold working rate of 60%)—a final annealing process (finalrecrystallization heat treatment process)—a finish cold rolling process(sheet thickness of 0.3 mm and a cold working rate of 17%)—a recoveryheat treatment were carried out.

As the final annealing of the processes A1-1 to 3, batch annealing (425°C., holding time: 4 hours) was carried out. In the process A1-1, arecovery heat treatment was carried out under batch-type conditions(300° C., holding time: 30 minutes) in a laboratory. In the processA1-2, a recovery heat treatment was carried out by a continuous hightemperature short time annealing method in a work line under theconditions of (450° C.-0.05 minutes) when the maximum reachingtemperature of the rolled material Tmax (° C.) and a holding time tm(min) in a range from a temperature 50° C. lower than the maximumreaching temperature of the rolled material to the maximum reachingtemperature are expressed as (Tmax (° C.)-tm (min or minutes)). In therecovery heat treatment of the process A1-3, a heat treatment, whichwill be described later, was carried out in a laboratory under theconditions of (300° C.-0.07 min). In the process A1-4, final annealingwas carried out under the conditions of (690° C.-0.14 minutes) of a hightemperature short time annealing method and (450° C.-0.05 minutes) of arecovery heat treatment.

In the processes A2-1 to A2-10, an annealing process was carried out onetime, and cold rolling (sheet thickness: 1 mm)—an annealing process arolling process before finishing (in the processes A2-1 to A2-4, andA2-10, sheet thickness: 0.36 mm, cold working rate: 64%, and in theprocesses A2-5 to A2-9, sheet thickness: 0.4 mm, cold working rate:60%)—a final annealing process—a finish cold rolling process (in theprocesses A2-1 to A2-4 and A2-10, sheet thickness: 0.3 mm, cold workingrate: 17%, and in the processes A2-5 to A2-9, sheet thickness: 0.3 mm,cold working rate: 25%)—a recovery heat treatment were carried out.

The annealing process of the processes A2-1 to A2-6 and A2-9 was carriedout under the conditions of (510° C., holding time: 4 hours) and theprocesses A2-7, A2-8 and A2-10 were carried out by a high temperatureshort time annealing method under the conditions of (670° C.-0.24minutes).

As the final annealing of the process A2-1, batch annealing (425° C.,holding time: 4 hours) was carried out, the processes A2-2, 3 and 4 werecarried out by a continuous high temperature short time annealing method(670° C.-0.09 minutes), the processes A2-5 and A2-6 were carried outunder the conditions of (690° C.-0.14 minutes), the process A2-7 wascarried out under the conditions of (705° C.-0.18 minutes), the processA2-8 was carried out under the conditions of (770° C.-0.25 minutes), theprocess A2-10 was carried out under the conditions of (620° C.-0.05minutes), and the process A2-9 was carried out under the conditions ofbatch annealing of (580° C., holding time: 4 hours).

In the continuous high temperature short time annealing method which hasbeen carried out, when the temperature is 600° C. or the maximumreaching temperature is 600° C. or lower, the average cooling rate in atemperature range from the maximum reaching temperature to 350° C. was3° C./second to 18° C./second although the average cooling rate differeddepending on conditions.

The recovery heat treatment of the processes A2-1, 2, 5, and 7 to 10 wascarried out under the conditions of continuous high temperature shorttime annealing of (450° C.-0.05 minutes), the process A2-3 was carriedout in a laboratory under the conditions of (300° C.-0.07 min), and theprocess A2-6 was carried out in a laboratory under the conditions of(250° C.-0.15 min). Regarding the process A2-4, the recovery heattreatment was not carried out.

The high temperature short time annealing was carried by a method ofcompletely immersing the rolled material in 2-liter oil baths storingheat treating oils, which are classified into 3 kinds in JIS in JIS K2242:2012, each heated to 300° C. and 250° C., for 0.07 minutes and 0.15minutes, respectively, under the conditions of (300° C.-0.07 min) or(250° C.-0.15 min) as conditions corresponding to a molten Sn platingprocess, instead of the recovery heat treatment.

The process A3-1 was carried out by cold-rolling a milling material to 1mm and carrying out a continuous high temperature short time annealingmethod under the conditions of (680° C.-0.3 minutes) such that theaverage grain size was 10 μm to 18 μm. The coil was slit to have a widthof 86 mm, and for production of a welded pipe, an intermediate material(annealed material of width 86 mmxthickness 1 mm) was supplied at a feedrate of 60 m/min and was subjected to deformation processing into acircular shape by plural rolls. The cylindrical material was heated by ahigh-frequency induction heating coil and the both ends of theintermediate material were joined by lamination. A welded pipe having adiameter of 25.4 mm and a thickness of 1.08 mm was obtained by cuttingand removing the bead portion of the joint portion by a cutting tool(cutting blade tool). Due to changes in thickness, when the welded pipeis formed, cold working of substantially several percents is carriedout.

In addition, the production process B was carried out as follows usingexperimental facilities.

Ingots of the production process A were cut into ingots for a laboratorytest which had a thickness of 30 mm, a width of 120 mm and a length of190 mm. Then, the cut ingots were subjected to a hot rolling process(sheet thickness: 6 mm)—a cooling process (air cooling)—a picklingprocess a rolling process—an annealing process—a rolling process beforefinish (thickness: 0.36 mm)—a recrystallization heat treatment process afinish cold rolling process (sheet thickness: 0.3 mm, working rate:17%)—a recovery heat treatment.

In the hot rolling process, each of the ingots was heated to 830° C. andthe ingot was hot-rolled to a thickness of 6 mm. The cooling rate(cooling rate at the temperature of a rolled material after the hotrolling or in a temperature range from 650° C. to 350° C.) in thecooling process was mainly set to 5° C./second, and the surface of therolled material was pickled after the cooling process.

In the processes B1-1 to B1-3, an annealing process was carried out onetime, a material was cold-rolled to 0.9 mm in a rolling process, theannealing process was carried out under the conditions of (510° C.,holding time: 4 hours), and the material was cold-rolled to 0.36 mm in arolling process before finishing. Final annealing was carried out underthe conditions of (425° C., holding time: 4 hours) in the process B1-1and (670° C.-0.09 minutes) in the processes B1-2 and B1-3, and thematerial was finish-rolled to 0.3 mm. Then, a recovery heat treatmentwas carried out under the conditions of (450° C.-0.05 minutes) in theprocess B1-1, (300° C.-0.07 min) in the process B1-2, and (300° C.,holding time: 30 minutes) in the process B1-3.

In the process B2-1, an annealing process was omitted. A sheet materialhaving a thickness of 6 mm after pickling was cold-rolled to 0.36 mm inthe rolling process before finishing (working rate: 94%), finalannealing was carried out under the conditions of (425° C., holdingtime: 4 hours), the material was finish-rolled to 0.3 mm, and further, arecovery heat treatment was carried out under the conditions of (300°C., holding time: 30 minutes).

In the processes B3-1 and B3-2, hot rolling was not carried out and coldrolling and annealing were repeatedly carried out. The ingot having athickness of 30 mm was subjected to homogenization annealing at 720° C.for 4 hours, cold-rolled to 6 mm, subjected to an annealing processunder the conditions of (620° C., holding time: 4 hours), cold-rolled to0.9 mm, subjected to an annealing process under the conditions of (510°C., holding time: 4 hours), and cold-rolled to 0.36 mm. Final annealingwas carried out under the conditions of (425°, holding time: 4 hours) inthe process of B3-1 and (670° C.-0.09 minutes) in the process of B3-2,the material was finish-cold-rolled to 0.3 mm, and then a recovery heattreatment was carried out under the conditions of (300° C., holdingtime: 30 minutes).

In the production process B, a process corresponding to a short-timeheat treatment performed by a continuous annealing line or the like inthe production process A was substituted with immersion of the rolledmaterial in a salt bath. The maximum reaching temperature was set to atemperature of a liquid of the salt bath, the immersion time was set tothe holding time, and air cooling was performed after immersion. Inaddition, a mixed material of BaCl, KCl, and NaCl was used as salt(solution).

Further, the process C (Cl, CIA) as a laboratory test was carried out asfollows. Melting and casting were carried out with an electric furnacein a laboratory to have predetermined components, whereby ingots for atest, which had a thickness of 30 mm, a width of 120 mm, and a length of190 mm, were obtained. Then, production was carried out by the sameprocesses as the above-described process B1-1. Each of the ingots washeated to 830° C. and hot-rolled to a thickness of 6 mm. After the hotrolling, the ingot was cooled at a cooling rate of 5° C./second at atemperature of the rolled material after the hot rolling or in atemperature range from 650° C. to 350° C. The surface of the rolledmaterial was pickled after the cooling, and the rolled material wascold-rolled in the cold rolling process to 0.9 mm. After the coldrolling, the annealing process was carried out under conditions of 510°C. and 4 hours. In the following rolling process, the material wascold-rolled to 0.36 mm. Final annealing was carried out under theconditions of (425° C., holding time: 4 hours) in the process C1 and(670° C.-0.09 minutes) in the process CIA, the material was cold-rolledto 0.3 mm (cold working rate: 17%) in the finish cold rolling, and arecovery heat treatment was carried out under the conditions of (300°C., holding time: 30 minutes).

The process C2 is a process of a material for comparison and due to thecharacteristics of the material, the thickness and heat treatmentconditions were changed such that the final average grain size was 10 μmor less and the tensile strength was about 500 N/mm². After pickling,the material was cold-rolled to 1 mm, an annealing process was carriedout under the conditions of 430° C. and 4 hours, and the material wascold-rolled to 0.4 mm in a rolling process. Final annealing conditionswere a temperature of 380° C. and a holding time of 4 hours, thematerial was cold-rolled to 0.3 mm by finish cold rolling, (cold workingrate: 25%), and a recovery heat treatment was carried out under theconditions of (230° C., holding time: 30 minutes).

Regarding phosphor bronze, a commercially available product of C5210containing 8 mass % of Sn and having a tensile strength of about 640N/mm² and a thickness of 0.3 mm was prepared.

The metallographic structures of the copper alloys prepared in theabove-described methods were observed, and the average grain size andthe ratios of β and γ phases were measured. In addition, the averageparticle size of precipitates was measured by TEM. Further, to evaluatethe characteristics of the copper alloys, tests for conductivity, stressrelaxation characteristics, stress corrosion cracking resistance,tensile strength, proof stress, elongation, bending workability, colorfastness, and antimicrobial properties were carried out for measuringthe characteristics.

<Structure Observation>

The average grain size of grains was measured according to planimetry ofmethods for estimating the average grain size of wrought copper andcopper alloys defined in JIS H 0501 by selecting an appropriatemagnification according to the size of grains based on metallographicmicroscopic images of, for example, magnifications of 300 times, 600times, and 150 times. Twin was not considered as a grain. The averagegrain size was calculated according to planimetry (JIS H 0501).

One grain is elongated by rolling, but the volume of the grain is notsubstantially changed by rolling. In cross-sections obtained by cuttinga sheet material in directions parallel to and perpendicular to arolling direction, an average grain size in the stage ofrecrystallization can be estimated from the average grain size measuredaccording to planimetry.

The ratio of an α phase of each material was determined from imagesobtained by a metallurgical microscope at a magnification of 300 times(micrographs of a view field of 89 mm×127 mm). When each material wasetched using a mixed solution of ammonia water and hydrogen peroxide andthe structure was observed by a metallurgical microscope, the α phasewas seen to be light yellow, the β phase was seen to be a yellow deeperthan the color of the α phase, the γ phase was seen to be light blue,oxides and non-metallic inclusions were seen to be gray, and coarsemetallic compounds were seen to be a light blue more bluish than thecolor of the γ phase or blue. Therefore, each phase of α, β and γ,non-metallic inclusions and the like is easily distinguished from eachother. The β and γ phases in the observed metallographic structure werebinarized using image processing software “Win ROOF” and the ratios ofthe areas of β and γ phases with respect to the total ratio of themetallographic structure were obtained as area ratios. Themetallographic structure was measured from three visual fields, and theaverage value of the respective area ratios was calculated. Regarding aseam welded pipe, the measurement was carried out in three visual fieldseach at a joint portion, a heat affected zone included in a heataffected zone 1 mm apart from the boundary between the joint portion andthe heat affected zone, and an arbitrary portion of a base material anda total of the average values thereof was divided by 3.

<Precipitate>

The average particle size of precipitates was obtained as follows.Transmission electronic microscopic images were obtained using a TEM ata magnification of 500,000 times and a magnification of 150,000 times(detection limits were 2.0 nm), and the contrast of a precipitate waselliptically approximated using image analysis software “Win ROOF”. Thegeometric average value of long and short axes was obtained from each ofall the precipitate particles in the field of view. The average valuethereof was obtained as an average particle size. Precipitates having anaverage size of about less than 5 nm were measured at 750,000 times (thedetection limit was 0.5 nm), and precipitates having an average size ofabout greater than 50 nm were measured at 50,000 times (the detectionlimit was 6 nm). In the case of a transmission electron microscope,since the cold-rolled material has a high dislocation density, it isdifficult to accurately obtain precipitate information. In addition, thesize of a precipitate is not changed by cold-rolling. Therefore, in thisobservation, recrystallized portions before the finish cold rollingprocess and after the recrystallization heat treatment process wereobserved. Two measurement positions were located at a depth of ¼ of thethickness of the sheet from both the front and rear surfaces of a rolledmaterial and the measured values of the two positions were averaged.

<Conductivity>

Conductivity was measured using a conductivity measuring device(SIGMATEST D2.068, manufactured by Foerster Japan Ltd.). In thisspecification, “electric conduction” has the same definition as that of“conduction”. In addition, thermal conduction has a strong relationshipwith electric conduction. Therefore, the higher the electricconductivity is, the higher the thermal conductivity is.

<Stress Relaxation Characteristics>

A stress relaxation rate was measured as follows. In a stress relaxationtest of a test material, a cantilever screw jig was used. Two testpieces were collected from a direction parallel with a rolling directionand a direction perpendicular to the rolling direction and had a shapeof thickness 0.3 mm×width 10 mmxlength 60 mm. A load stress on the testmaterial was set to be 80% with respect to a 0.2% proof stress testmaterial that was exposed to an atmosphere of 150° C. and 120° C. for1,000 hours. The stress relaxation rate was obtained from the followingexpression.

Stress relaxation rate=(displacement after relief/Displacement underload stress)×100(%)

The average value of test pieces which were collected from bothdirections parallel with and perpendicular to the rolling direction wasused. In the present invention, it is desired to obtain particularlyexcellent stress relaxation characteristics even in a Cu—Zn alloycontaining a high concentration of Zn. Therefore, when the stressrelaxation rate at 150° C. is 25% or less, stress relaxationcharacteristics are excellent. When the stress relaxation rate is morethan 25% and 35% or less, stress relaxation characteristics aresatisfactory and when the rate is more than 35% and 50% or less, thereis a problem in use. When the rate is more than 50%, there aredifficulties in use. Particularly, when the rate is more than 70%, thereis a significant problem in use in a high temperature environment andthe sample is “not available”.

On the other hand, in a test under slightly mild conditions of 120° C.and 1,000 hours, higher performance is required. In a case in which thestress relaxation rate was 10% or less, the level of stress relaxationcharacteristics was high and this case was evaluated as “A”. In a casein which the stress relaxation rate was more than 10% and 15% or less,stress relaxation characteristics were satisfactory and this case wasevaluated as “B”. In a case in which the stress relaxation rate was morethan 15% and 30% or less, there was a problem in use. In a case in whichthe stress relaxation rate was more than 30%, the test piece wassubstantially mild and there was little superiority as a material. Inthe specification, it is desired to obtain particularly excellent stressrelaxation and thus the test piece having a stress relaxation rate ofmore than 15% was evaluated as “C”.

On the other hand, the maximum effective contact pressure is expressedby proof stress×80%×(100%−stress relaxation rate (%)). In the alloy ofthe present invention, it is important that not only proof stress atroom temperature be high or the stress relaxation rate be low, but alsothe value of the above expression be high. An alloy in which the valueof proof stress×80%×(100%−stress relaxation rate (%)) is 275 N/mm² ormore in the test at 150° C. can be used in a high temperature state andan alloy in which the value is 300 N/mm² or more is suitably used in ahigh temperature state. An alloy in which the value is 325 N/mm² or moreis most suitable. In applications of yellow brass containing a largeamount of Zn such as terminals and connectors, in the specification, itis desired to obtain color fastness which endures a severe hightemperature and excellent stress relaxation characteristics and thus ahigh stress relaxation rate at 120° C. and 150° C. for 1,000 hours, orhigh effective stress is desired. In the specification, as proof stressand a stress relaxation rate, the average values of proof stress andstress relaxation rates of test pieces collected from two directionsparallel with and perpendicular to the rolling direction are used. Theproof stress and stress relaxation characteristics may not be obtainedfrom a direction which forms 90 degrees (perpendicular) with respect tothe rolling direction due to the relation with the width of a slit afterbeing slit, that is, when the width is smaller than 60 mm. In this case,only from a direction which forms 0 degree (parallel) with respect tothe rolling direction, the stress relaxation characteristics and themaximum effective contact pressure (effective stress) of a test pieceare evaluated.

In test Nos. 31, 34 and 36 (Alloy No.3) and test Nos. 50, 54 and 54A(Alloy No. 4), it was confirmed that there was no significant differenceamong the effective stress calculated from the results of the stressrelaxation test in a direction which forms 90 degrees (perpendicular)with respect to the rolling direction and a direction which forms 0degree (parallel) with respect to the rolling direction, the effectivestress calculated from the results of the stress relaxation test only ina direction which forms 0 degree (parallel) with respect to the rollingdirection, and the effective stress calculated from the results of thestress relaxation test only in a direction which forms 90 degrees(perpendicular) with respect to the rolling direction.

<Stress Corrosion Cracking 1>

Stress corrosion cracking properties were measured by adding sodiumhydroxide and pure water to a test solution, that is, ammonium chlorideby using a test container defined in ASTM B858-01 (107 g/500 ml) toadjust the pH to 10.1±0.1, and the air conditioning in a room wascontrolled to 23° C±1° C.

First, bending plastic working and residual stress were applied to arolled material and stress corrosion cracking properties were evaluated.Using a bending workability evaluation method, which will be describedlater, a test piece which was subjected to W bending at R (radius: 0.6mm) of two times the thickness of a sheet was exposed to the stresscorrosion cracking environment. After a predetermined period of exposuretime, the test piece was taken out and washed with sulfuric acid. Then,whether cracking occurred or not was investigated using a stereoscopicmicroscope at a magnification of 10 times (visual field of 200 mm×200mm, substantially, 20 mm×20 mm (actual size)) to evaluate stresscorrosion cracking resistance. Samples collected from a directionparallel with a rolling direction were used. A test piece in whichcracking had not occurred through exposure for 48 hours had excellentstress corrosion cracking resistance and was evaluated as “A”. A testpiece in which little cracking had occurred through exposure for 48hours but cracking had not occurred through exposure for 24 hours hadsatisfactory stress corrosion cracking resistance (without any problemin practical use) and was evaluated as “B”. A test piece in whichcracking occurred through exposure for hours had deteriorated stresscorrosion cracking resistance (with a problem in practical use) and wasevaluated as “C”.

Regarding a seam welded pipe, a sample which was crushed until adistance between flat sheets in a flattening test, which will bedescribed later, became 5 times the thickness of the pipe was used.

<Stress Corrosion Cracking 2>

In addition, stress corrosion cracking properties were evaluated byanother method separately from the above-described evaluation.

In the stress corrosion cracking test, in order to investigatesensitivity for stress corrosion cracking in a state in which stress wasapplied, a resin cantilever screw type jig was used. A rolled materialwas exposed to the stress corrosion cracking atmosphere in a state inwhich as in the stress relaxation test, bending stress which was 80% ofproof stress, that is, stress of the elastic limit of the material wasapplied, and stress corrosion cracking resistance was evaluated from thestress relaxation rate. That is, when minute cracking occurs, and adegree of the cracking increases without returning to the originalstate, the stress relaxation rate increases, and thus the stresscorrosion cracking resistance can be evaluated. A test piece in whichthe stress relaxation rate through exposure for 24 hours was 15% or lesshad excellent stress corrosion cracking resistance and was evaluated as“A”. A test piece in which the stress relaxation rate was more than 15%and 30% or less had satisfactory stress corrosion cracking resistanceand was evaluated as “B”. The use of a test piece in which the stressrelaxation rate was more than 30% under a severe stress corrosioncracking environment was difficult and the sample was evaluated as “C”.The samples used were collected from a direction parallel with a rollingdirection were used.

<Mechanical Properties and Bending Workability of Sheet Material>

The tensile strength, proof stress, and elongation of the sheet materialwere measured according to methods defined in JIS Z 2201 and JIS Z 2241and a No. 5 test piece was used regarding the shape of a test piece.Test pieces were collected from two directions parallel with andperpendicular to the rolling direction. Here, the width of the materialstested in the processes B and C was 120 mm and a test piece according tothe No. 5 test piece was used.

The bending workability of a sheet material was evaluated in a W bendingtest defined in JIS H 3110. The bending (W-bending) test was carried outas follows. A bending radius was set to be one time (bending radius=0.3mm, 1 t) and 0.5 times (bending radius=0.15 mm, 0.5 t) the thickness ofa material. Samples were bent in a direction, in a so-called bad way,which forms 90 degrees with a rolling direction and in a direction, in aso-called good way, which forms 0 degrees with the rolling direction. Inthe evaluation of bending workability, whether cracking occurred or notwas determined by observation using a stereoscopic microscope at amagnification of 20 times (view field of 200 mm×200 mm, substantially,10 mm×10 mm (actual size)). A test piece in which cracking had notoccurred when the bending radius was 0.5 times the thickness of amaterial was evaluated as “A”. A test piece in which cracking had notoccurred when the bending radius was 1 time the thickness of a materialwas evaluated as “B”. A test piece in which cracking had occurred whenthe bending radius was 1 time the thickness of a material was evaluatedas “C”.

<Mechanical Properties and Workability of Seam Welded Pipe>

For the mechanical properties of a seam welded pipe, a tensile test wascarried out by using a No. 11 test piece of a metal material tensiletest piece of JIS Z 2241 (gauge length: 50 mm, the test piece was usedin a state in which the test piece was cut from the pipe material) andinserting a core bar into a grip portion.

First, the joint portion of the seam welded pipe was evaluated bycarrying out a flattening test described in JIS H 3320 on a copper orcopper alloy welded pipe. A sample was collected from a portion about100 mm apart from the end of the seam welded pipe, the sample wasinterposed between two flat sheets and was crushed until a distancebetween the flat sheets became three times the thickness of the pipe. Atthis time, the joint portion of the seam welded pipe was arranged in adirection perpendicular to the compression direction and was subjectedto flattening bending so that the joint portion became a tip end ofbending. The state of the joint portion which was subjected to bendingwas visually observed. Next, a flaring test was carried out by a methoddescribed in JIS H 3320. In the flaring test, a conical tool with avertical angle of 60° was pushed into one end of a sample of 50 mm cutfrom the welded pipe until a diameter of 1.25 times the outer diameter(that is, a diameter of 31.8 mm which was 1.25 times the diameter of theend portion of 25.4 mm by the flaring) was obtained and cracking of thewelded portion was visually confirmed. Regarding the evaluation of bothtests, a test piece in which defects such as cracking and minute holeswere not observed was evaluated as “A” and a test piece which was notavailable due to defects such as cracking and holes occurred in thejoint portion was evaluated as “C”.

<Color Fastness Test 1: High Temperature High Humidity Environment Test>

In the color fastness to evaluate the color fastness of a material,using a thermo-hygrostat (HIFLEX FX2050, produced by Kusumoto Chemicals,Ltd.), each sample was exposed to an atmosphere at a temperature of 60°C. and a relative humidity of 95%. As a test piece, a test piece beforea final recovery heat treatment is carried out, that is, a sheetmaterial after finish rolling was used. The test time was set to 72hours. The sample was taken out after the test, L*a*b* values of thesurface color of the material before and after the exposure weremeasured by a spectrophotometer, and the color difference was calculatedand evaluated. In copper and a copper alloy, particularly, a Cu—Zn alloycontaining a high concentration of Zn, the color changes to reddishbrown or red. Due to this, for the evaluation of color fastness, asample in which a difference between a* values before and after thetest, that is, a value of a change in an a* value was 1 or less, wasevaluated as “A”. A sample in which the difference was greater than 1and 2 or less was evaluated as “B”. A sample in which the difference wasgreater than 2 was evaluated as “C”. It could be determined that as thenumerical value increases, the color fastness deteriorates, and visualevaluation was also matched with the results.

<Color Fastness Test 2: High Temperature Test>

On the assumption of a room, particularly, a cabin of an automobile andan engine room under the severe blazing sun, color fastness at a hightemperature was evaluated. As a test piece, a sheet material before afinal recovery heat treatment was carried out was used. In theatmosphere, the test piece was held in an electric furnace at 120° C.for 100 hours and L*a*b* values of the surface color before and afterthe test were measured by a spectrophotometer. As in the above test, forthe evaluation of color fastness, a sample in which a difference betweena* values before and after the test, that is, a value of a change in ana^(k) value was 3 or less was evaluated as “A”. A sample in which thedifference was greater than 3 and 5 or less was evaluated as “B”. Asample in which the difference was greater than 5 was evaluated as “C”.

<Color Tone and Color Difference>

The surface color (color tone) of the copper alloy to be evaluated inthe color fastness test was expressed using a method of measuring anobject color according to JIS Z 8722-2009 (Methods of colormeasurement-Reflecting and transmitting objects) and the L*a*b colorsystem defined in JIS Z 8729-2004 (Color specification-L*a*b colorsystem and L*u*v* color system). Specifically, a spectrophotometer“CM-700d”, produced by Konica Minolta, Inc. was used and the L*a*b*values before and after the test were measured at 3 points by a SCI(including specular reflection light) method.

<Antimicrobial Properties>

The antimicrobial properties (bactericidal properties) were evaluated bya test method referring to JIS Z 2801 (Antimicrobial products-Test forantimicrobial activity and efficacy) and a film contact method, and thetest area (film area) and the contact time were changed to conductevaluation. Escherichia coli (stock No. of strain: NBRC3972) was used asthe bacteria for the test. A solution, which was obtained byprecultivating (as the preculture method, a method described in 5.6.a ofJIS Z 2801 was used) Escherichia coli at 35° C.±1° C. and dilutingEscherichia coli with 1/500 NB to adjust the number of bacteria to1.0×10⁶ cells/mL, was used as a test bacterial suspension. In the testmethod, samples were obtained by cutting from the sheet material afterfinish rolling, the sample after the high temperature high humidity testat 60° C. and a humidity of 95%, and the sample after the hightemperature test at 120° C. for 100 hours into 20 mm×20 mm. Each samplewas put into a sterilized petri dish, 0.045 mL of the above-describedtest bacterial suspension (Escherichia coli: 1.0×10⁶ cells/mL) was addeddropwise thereto, and the petri dish was covered with a φ15 mm film andthen covered with a lid. The test bacterial suspension was cultivatedfor 10 minutes (inoculation time: 10 minutes) in the petri dish in anatmosphere of 35° C.±1° C. and a relative humidity of 95%. Thiscultivated test bacterial suspension was washed away with 10 mL of SCDLPculture medium to obtain a wash-away bacterial suspension. The wash-awaybacterial suspension was diluted 10 times with a phosphate bufferedsaline solution. Standard plate count agar was added to this bacterialsuspension, followed by cultivation at 35° C.±1° C. for 48 hours. Whenthe number of colonies was more than or equal to 30, the number ofcolonies was measured to obtain the viable bacterial count (cfu/mL). Thenumber of colonies at the time of inoculation (the bacterial count whenthe test for antimicrobial properties started; cfu/mL) was set as acriterion.

First, the viable bacterial count of each sample after the finishrolling was carried out was compared to the viable bacterial count. Acase in which the rate was less than 10% was evaluated as “A”. A case inwhich the rate was 10% to less than 33% was evaluated as “B”. A case inwhich the rate was 33% or more was evaluated as “C”. For samples whichwere evaluated as A (that is, the viable bacterial count of theevaluation sample was less than 1/10 of the viable bacterial count atthe time of inoculation), antimicrobial properties (bactericidalproperties) were evaluated to be excellent, and for samples which wereevaluated as B (that is, the viable bacterial count of the evaluationsample was less than ⅓ of the viable bacterial count at the time ofinoculation), antimicrobial properties (bactericidal properties) wereevaluated to be satisfactory. The reason why the culture time(inoculation time) at 10 minutes was short is that the immediateactivity for antimicrobial properties (bactericidal properties) wasevaluated.

Next, in the evaluation of antimicrobial properties (bactericidalproperties), a case in which the relationship between a viable bacterialrate C_(H) obtained from the samples after the two color fastness testsand a case in which a viable bacterial rate C₀ before the color fastnesstests was C_(H)≤1.10×C₀ was evaluated as “A”, a case in which therelationship was 1.10×C₀<C_(H)≤1.25×C₀ was evaluated as “B”, and a casein which the relationship was C_(H)>1.25×C₀ was evaluated as “C”. Thatis, when the color of the copper alloy is changed, there is a concern oflowering of antimicrobial performance. In the alloy of the presentinvention, a slight color change by the severe test at a hightemperature and high humidity or at a high temperature is observed andthe formation of oxides and the like on the outermost surface layer ofthe surface is predicted. In these samples whose color is slightlychanged, compared to a sample having a clean surface before the tests,the antimicrobial performance of a sample evaluated as A or at least Bis not impaired.

In addition, separately from the above evaluation, antimicrobialproperties were evaluated in the following method. As a test piece(container), a material for a seam welded pipe having a thickness of 1mm was used and the sheet material was punched by a punch to have a holeof φ125 mm. The punched sheet material was formed into a cup shapehaving a bottom surface of φ80 mm and a height of 50 mm by metalspinning, and washed and degreased with acetone for about 5 minutes byultrasonic washing. A total three samples of one test piece which wasused after the test piece was formed and two other test pieces of asample obtained by subjecting a high temperature high humidity testhaving conditions of a temperature of 60° C. and humidity of 95% to thecup-shaped test piece and a sample obtained by subjecting a hightemperature test having conditions of a temperature of 120° C. for 100hours to the cup-shaped test piece were prepared. Regarding Alloy No.201 as a comparative material, a material which had been sampled at astage of 1 mm and has been subjected to a heat treatment at 430° C. for4 hours was used.

In the antimicrobial property test, Escherichia coli (NBRC3972) wereshake-cultured in 5 mL of a normal broth culture medium for one night at27° C. and then 1 mL of the culture medium was centrifugally separatedto obtain bacterial cells. The bacterial cells were suspended in 1 mL ofsterilized saline solution (0.85%) and the suspension was diluted 1,200times with sterilized water including the normal broth culture medium toa final concentration of 1/500. 200 mL of a suspension of a viablebacterial count of Escherichia coli of about 8×10⁶ cfu/mL was pouredinto each of the above three kinds of test containers and left atair-conditioned room temperature (about 25° C.). After 4 hours, 0.05 mLof the suspension was collected to 4.95 mL of SCDLP culture medium“DAIGO” and diluted 10 times with 4 stages. Then, the viable bacterialcount in 1 mL of each suspension was measured. When the viable bacterialcount before the test was compared to the the viable bacterial countafter 4 hours, a case in which the rate was less than 3% was evaluatedas “A”. A case in which the rate was 3% to less than 10% was evaluatedas “B”. A case in which the rate was 10% or more was evaluated as “C”.For samples which were evaluated as A (that is, the viable bacterialcount of the evaluation sample was less than 1/33 of the viablebacterial count at the time of inoculation), antimicrobial properties(bactericidal properties) were evaluated to be excellent, and forsamples which were evaluated as B (that is, the viable bacterial countof the evaluation sample was less than 1/10 of the viable bacterialcount at the time of inoculation), antimicrobial properties(bactericidal properties) were evaluated to be satisfactory. Theevaluation of maintaining antimicrobial properties (bactericidalproperties) based on color change was carried out using the viablebacterial rate C_(H).

That is, when the initial sample of the finish rolled material wasevaluated as “A” and the sample after the severe test was also evaluatedas “A” or at least “B”, sufficient antimicrobial performance andbactericidal performance were provided in actual used apparatuses andmetal fittings. A material suitable for applications such aspublic-based use such as public facilities, hospitals, welfarefacilities, and vehicles, handrails, door handles, door knobs, and doorlevers, which many people use in a building or the like, medicalappliances, medical containers, headboards, footboards, and water supplyand drain sanitary facilities and apparatuses such as a drainage tankused in vehicles and the like can be obtained.

The evaluation results of the sheet materials are shown in Tables 6 to25. The evaluation results of the seam welded pipes are shown in Table26. The evaluation results of antimicrobial properties are shown inTables 27 and 28.

TABLE 6 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150° C. × 120° C. × Stress corrosion cracking ofαgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/mm²) (Evaluation)(Evaluation) 1 A1-1 1 100 4 — 17 25 A 340 A B 2 A1-2 100 4 — 17 26 B 333A B 3 A1-3 100 4 — 17 28 B 327 A B 4 A1-4 100 7 — 17 23 A 334 A B 5 A2-1100 5 — 17 25 B 335 A B 6 A2-2 100 5 — 17 23 A 341 A B 7 A2-3 100 5 — 1725 B 336 A B 8 A2-4 100 5 — 16 — — — A B 9 A2-5 100 6 — 17 23 A 365 A B  9A A2-6 100 6 — 17 28 B 344 A B   9B A2-7 100 9 — 16 24 A 341 A B   9CA2-8 100 30 — 16 27 B 295 B B   9D A2-10 100 1.5 — 17 27 B 367 A B 11 B1-1 100 5 — 17 25 B 335 A B 12  B1-2 100 5 — 17 27 B 329 A B 13  B1-3100 5 — 17 23 A 344 A B 14  B2-1 100 5 — 17 25 B 343 A B 15  B3-1 100 6— 17 26 B 321 A B  15A B3-2 100 6 — 17 26 B 322 A B

TABLE 7 Color fastness Direction parallel with Direction orthogonal toHigh rolling direction rolling direction Bending workability temperatureTensile Proof Tensile Proof Good Bad high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm²) (%) ation) ation)(Evaluation) (Evaluation) 1 A1-1 1 609 562 15 623 572 12 A A A A 2 A1-2612 566 14 618 560 11 A A — — 3 A1-3 618 573 13 622 562 10 A A — — 4A1-4 579 539 22 590 546 16 A A — — 5 A2-1 594 555 18 616 562 11 A A A A6 A2-2 584 548 18 615 560 12 A A — — 7 A2-3 596 555 16 622 564 11 A A —— 8 A2-4 590 549 18 609 526 12 A A A A 9 A2-5 633 586 11 659 598 9 A B ——   9A A2-6 645 598 10 672 595 7 A B — —   9B A2-7 600 552 12 622 570 11A B A A   9C A2-8 538 476 13 576 533 12 A B — —   9D A2-10 652 601 9 706656 6 B C — — 10  A3-1 488 392 42 — — — A A — — 11  B1-1 595 551 17 615565 12 A A A A 12  B1-2 604 565 16 618 560 11 A A — — 13  B1-3 589 55018 615 567 12 A A — — 14  B2-1 603 562 16 628 580 11 A A A A 15  B3-1584 538 20 604 547 13 A A A A  15A B3-2 580 539 19 602 550 13 A A A A

TABLE 8 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150° C. × 120 ° C. × Stress corrosion cracking of αgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/mm²) (Evaluation)(Evaluation) 16 A1-1 2 100 3 — 15 21 A 366 A A 17 A1-2 100 3 — 15 22 A362 A A 18 A1-3 100 3 — 15 25 B 349 A A 19 A1-4 100 6 — 15 20 A 352 A A20 A2-1 100 4 — 15 21 A 361 A A 21 A2-2 100 4 — 15 20 A 364 A A 22 A2-3100 4 — 15 23 A 354 A A 23 A2-4 100 4 — 15 — — — A A 24 A2-5 100 6 — 1520 A 388 A A 26 B1-1 100 4 — 15 21 A 361 A A 27 B1-2 100 4 — 15 23 A 356A A 28 B1-3 100 4 — 15 20 A 360 A A 29 B2-1 100 3 — 15 21 A 366 A A 30B3-1 100 5 — 15 22 A 347 A A   30A B3-2 100 5 — 15 21 A 351 A A

TABLE 9 Color fastness Direction parallel with Direction orthogonal toHigh rolling direction rolling direction Bending workability temperatureTensile Proof Tensile Proof Good Bad high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm²) (%) ation) ation)(Evaluation) (Evaluation) 16 A1-1 2 622 577 15 636 582 11 A A A A 17A1-2 625 581 13 632 579 10 A A — — 18 A1-3 632 585 12 638 578 10 A A — —19 A1-4 591 550 20 603 550 15 A A — — 20 A2-1 607 564 17 630 578 11 A AA A 21 A2-2 609 561 17 626 575 11 A A — — 22 A2-3 615 574 16 632 574 10A A — — 23 A2-4 605 563 16 622 541 11 A A A A 24 A2-5 642 602 11 668 612 8 A B — — 25 A3-1 531 445 36 — — — A A — — 26 B1-1 604 565 17 626 57611 A A A A 27 B1-2 617 574 15 626 581 10 A A — — 28 B1-3 592 554 17 624572 12 A A — — 29 B2-1 616 573 15 641 585 10 A A A A 30 B3-1 598 552 18617 559 12 A A A A   30A B3-2 592 551 18 612 560 12 A A A A

TABLE 10 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150° C. × 120° C. × Stress corrosion cracking of αgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/mm²) (Evaluation)(Evaluation) 31 A1-1 3 100 3 40 16 16 A 395 A B 32 A1-2 100 3 40 16 16 A397 A B 33 A1-3 100 3 40 15 18 A 395 A B 34 A1-4 100 6 50 16 12 A 394 AB 35 A2-1 100 4 40 16 16 A 392 A B 36 A2-2 100 4 35 16 13 A 404 A B 37A2-3 100 4 35 15 15 A 396 A B 38 A2-4 100 4 40 15 — — — A B 39 A2-5 1006 60 16 13 A 429 A B 41 B1-1 100 4 40 16 16 A 392 A B 42 B1-2 100 4 3015 15 A 399 A B 43 B1-3 100 4 30 16 12 A 408 A B 44 B2-1 100 3 35 16 18A 388 A B 45 B3-1 100 5 60 16 18 A 373 A B   45A B3-2 100 5 55 16 13 A396 A B

TABLE 11 Direction parallel with Direction orthogonal to Color fastnessrolling direction rolling direction Bending workability High TensileProof Tensile Proof Good Bad temperature high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm²) (%) ation) ation)(Evaluation) (Evaluation) 31 A1-1 3 635 586 13 643 590 10 A B A A 32A1-2 633 589 13 646 592 10 A B — — 33 A1-3 640 597 12 662 606 9 A B — —34 A1-4 603 556 20 615 562 16 A A — — 35 A2-1 624 580 16 638 586 11 A BA A 36 A2-2 617 577 17 635 583 12 A A — — 37 A2-3 621 579 15 640 586 9 AB — — 38 A2-4 616 580 16 634 552 11 A B A A 39 A2-5 651 611 11 686 622 9A B — — 41 B1-1 617 578 16 637 588 11 A B A A 42 B1-2 627 581 15 648 59310 A B — — 43 B1-3 613 575 16 638 585 12 A A — — 44 B2-1 628 587 14 655597 10 A B A A 45 B3-1 613 566 18 630 570 12 A A A A   45A B3-2 609 56318 625 574 12 A A A A

TABLE 12 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150° C. × 120° C. × Stress corrosion cracking of αgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/mm²) (Evaluation)(Evaluation) 46 A1-1 4 100 3 40 19 19 A 367 A A 47 A1-2 100 3 40 19 19 A367 A A 48 A1-3 100 3 40 19 22 A 358 A A 49 A1-4 100 6 50 19 15 A 364 AA 50 A2-1 100 4 40 19 19 A 362 A A 51 A2-2 100 4 30 19 16 A 375 A A 52A2-3 100 4 30 19 18 A 371 A A 53 A2-4 100 4 30 18 — — — A A 54 A2-5 1006 50 19 14 A 408 A A   54A A2-6 100 6 50 18 19 A 392 A A   54B A2-7 1008 70 18 16 A 378 A A   55C A2-8 100 30 200 18 26 B 297 A A   55D A2-9100 12 220 20 28 B 306 A B  56E A2-10 100 1.5 6 19 20 A 404 A A 56 B1-1100 4 40 19 19 A 364 A A 57 B1-2 100 4 30 18 19 A 366 A A 58 B1-3 100 430 18 15 A 378 A A 59 B2-1 100 3 30 19 20 A 366 A A 60 B3-1 100 5 60 1920 A 348 A A   60A B3-2 100 5 — 19 16 A 370 A A

TABLE 13 Color fastness Direction parallel with Direction orthogonal toHigh rolling direction rolling direction Bending workability temperatureTensile Proof Tensile Proof Good Bad high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm²) (%) ation) ation)(Evaluation) (Evaluation) 46 A1-1 4 608 564 15 620 570 11 A A A A 47A1-2 611 566 14 621 568 10 A A — — 48 A1-3 620 573 13 634 576 9 A A — —49 A1-4 577 536 20 588 536 16 A A — — 50 A2-1 594 552 17 613 565 11 A AA A 51 A2-2 592 555 18 610 561 12 A A — — 52 A2-3 603 568 17 622 563 10A A — — 53 A2-4 590 548 17 609 528 11 A A A A 54 A2-5 630 586 11 662 6019 A A — —   54A A2-6 643 598 9 675 611 7 A B — —   54B A2-7 595 552 12618 572 10 A A A A 55 A3-1 470 372 41 — — — A A — —   55C A2-8 533 47213 574 530 11 A B — —   55D A2-9 563 500 12 622 562 8 A B — —  56E A2-10658 601 9 717 660 6 B C — — 56 B1-1 594 558 18 616 564 11 A A A A 57B1-2 601 562 17 620 569 10 A A — — 58 B1-3 587 548 18 612 563 12 A A — —59 B2-1 604 566 15 633 577 10 A A A A 60 B3-1 585 538 19 607 550 13 A AA A   60A B3-2 590 543 18 608 558 12 A A — —

TABLE 14 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150° C. × 120° C. × Stress corrosion cracking of αgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/mm²) (Evaluation)(Evaluation) 61 A2-1 5 100 4 50 21 20 A 351 A A 62 A2-2 100 4 — 21 15 A370 A A 63 A2-3 100 4 — 21 19 A 362 A A 64 A2-4 100 4 — 20 — — — A A 65A2-5 100 6 — 21 14 A 402 A A 67 B1-1 100 4 50 21 20 A 351 A A 68 B1-2100 4 — 21 19 A 360 A A 69 B1-3 100 4 — 21 14 A 375 A A 70 B2-1 100 4 4021 22 A 348 A A 71 B3-1 100 5 60 21 20 A 342 A A   71A B3-2 100 5 — 2116 A 360 A A 72 A2-1 6 100 3 35 18 17 A 379 A A   72A A2-2 100 3 — — 14A 392 A A 74 B1-1 100 4 35 18 15 A 377 A B 75 A2-1 7 100 4 — 16 21 A 358A A 77 B1-1 100 4 — 17 23 A 345 A A 78 A2-1 8 100 3 35 18 28 B 333 A B  78A A2-2 99.9 4 — — 30 B 321 B B 80 B1-1 100 4 40 18 27 B 327 A B

TABLE 15 Color fastness Direction parallel with Direction orthogonal toHigh rolling direction rolling direction Bending workability temperatureTensile Proof Tensile Proof Good Bad high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm²) (%) ation) ation )(Evaluation) (Evaluation) 61 A2-1 5 580 546 17 601 550 11 A A A B 62A2-2 579 540 18 596 548 12 A A — — 63 A2-3 592 561 16 606 556 10 A A — —64 A2-4 580 540 17 595 518 11 A A A B 65 A2-5 618 576 12 654 593 9 A A —— 67 B1-1 580 542 18 603 555 11 A A A B 68 B1-2 590 547 17 613 565 9 A A— — 69 B1-3 576 538 18 599 553 12 A A — — 70 B2-1 590 552 16 614 563 10A A A B 71 B3-1 572 531 19 593 538 12 A A A B   71A B3-2 570 530 19 588540 12 A A — — 72 A2-1 6 610 568 16 626 574 11 A A A A   72A A2-2 606563 16 622 576 11 A A A A 74 B1-1 595 552 19 611 558 13 A A A A 75 A2-17 604 564 15 622 569 12 A A A A 77 B1-1 592 553 18 615 566 13 A A A A 78A2-1 8 618 576 15 640 580 10 A B A A   78A A2-2 614 572 15 635 576 9 A B— — 80 B1-1 599 556 16 623 563 10 A B A A

TABLE 16 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150° C. × 120° C. × Stress corrosion cracking of αgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/nm²) (Evaluation)(Evaluation) 101 C1 11 100 5 — 17 30 B 319 B B 102 C1 12 100 4 — 19 26 B340 B B 103 C1 13 100 4 — 18 27 B 339 A B 104 C1 14 100 4 30 18 20 A 364B B 105 C1 15 100 5 — 17 28 B 321 B B 106 C1 16 100 3 25 20 21 A 355 A B  106A C1A 16 100 3 30 19 17 A 372 A B 107 C1 17 100 4 — 15 22 A 353 A B108 C1 18 100 4 — 20 22 A 342 A A 109 C1 19 100 4 — 17 23 A 345 A A 110C1 20 100 4 — 22 29 B 309 A B 111 C1 21 100 4 — 14 19 A 362 A A 112 C122 100 3 — 18 15 A 379 A A 113 C1 23 100 5 — 19 24 A 328 A A 114 C1 24100 5 — 22 28 B 308 A A 115 C1 25 100 4 — 14 23 A 349 A A 116 C1 26 1005 — 18 22 A 341 A A 117 C1 27 100 4 — 18 17 A 366 A A   117A C1A 27 1004 — 17 13 A 385 A A

TABLE 17 Color fastness Direction parallel with Direction orthogonal toHigh rolling direction rolling direction Bending workability temperatureTensile Proof Tensile Proof Good Bad high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm²) (%) ation) ation)(Evaluation) (Evaluation) 101 C1 11 602 563 16 636 578 10 A B A A 102 C112 612 569 16 643 580 10 A B B B 103 C1 13 623 577 15 643 583 10 A B A B104 C1 14 607 565 16 631 574 11 A A A A 105 C1 15 598 550 17 621 563 12A A A A 106 C1 16 604 558 16 624 565 10 A A B B   106A C1A 16 600 555 17622 565 11 A A A B 107 C1 17 605 560 17 629 571 11 A A A A 108 C1 18 588543 17 610 554 12 A A A B 109 C1 19 600 557 17 623 564 11 A A A A 110 C120 582 550 18 592 537 12 A A B B 111 C1 21 600 554 17 618 563 11 A A A A112 C1 22 600 552 16 620 564 11 A B A A 113 C1 23 583 534 18 600 545 12A A A A 114 C1 24 568 526 18 586 544 12 A A B B 115 C1 25 605 563 16 626571 10 A A A A 116 C1 26 580 541 17 604 551 12 A A A B 117 C1 27 589 54018 621 563 12 A A A A   117A C1A 27 590 542 19 624 565 12 A A A A

TABLE 18 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150° C. × 120° C. × Stress corrosion cracking of αgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/mm²) (Evaluation)(Evaluation) 118 C1 28 100 3 20 19 19 A 369 A B 119 C1 29 100 2.5 10 1821 A 366 A B 120 C1 30 100 3 15 18 19 A 369 A A 121 C1 31 100 3 — 17 25A 340 A B 122 C1 32 100 4 — 16 24 A 341 A B 123 C1 33 100 3 — 16 17 A388 B B 124 C1 34 100 4 — 18 19 A 363 A B 125 C1 35 100 3 — 17 25 A 341A B 126 C1 36 100 3 — 19 19 A 369 A B 127 C1 37 100 4 — 16 24 A 340 A B128 C1 38 100 4 — 16 17 A 384 A A 129 C1 39 100 4 — 17 25 B 338 A A 130C1 40 100 4 — 18 19 A 360 B B 131 C1 41 100 4 — 15 21 A 362 A A 132 C142 100 4 — 16 24 A 342 A A 133 C1 43 100 5 — 21 26 B 307 A B 134 C1 44100 3 — 18 27 B 334 A B 135 C1 45 100 4 — 17 20 A 364 A A

TABLE 19 Color fastness Direction parallel with Direction orthogonal toHigh rolling direction rolling direction Bending workability temperatureTensile Proof Tensile Proof Good Bad high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm²) (%) ation) ation)(Evaluation) (Evaluation) 118 C1 28 604 567 17 626 573 10 A A A B 119 C129 619 568 16 640 591 10 A B A A 120 C1 30 609 568 16 631 572 10 A A A A121 C1 31 603 558 16 632 575 10 A A A A 122 C1 32 595 556 17 620 565 11A A A A 123 C1 33 623 583 15 645 587 10 A B A A 124 C1 34 598 553 18 617566 12 A A A A 125 C1 35 608 563 16 632 574 11 A A A A 126 C1 36 606 56816 630 570 11 A A A B 127 C1 37 593 553 18 621 565 12 A A A A 128 C1 38614 574 16 634 582 11 A B A A 129 C1 39 602 558 17 624 570 11 A A A A130 C1 40 597 551 19 618 561 11 A A A A 131 C1 41 608 569 17 632 575 11A A A A 132 C1 42 600 558 17 626 567 12 A A A A 133 C1 43 553 513 17 571524 13 A A B B 134 C1 44 613 561 15 642 582 11 A B A B 135 C1 45 610 56516 630 572 11 A A A A

TABLE 20 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150° C. × 120° C. × Stress corrosion cracking of αgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/mm²) (Evaluation)(Evaluation) 201 A2-1 101 99.6 4 — 17 42 C 267 C C 202 A2-2 99.5 4 — 1743 C 261 C C 203 A2-3 99.5 4 — 17 48 C 242 C C 204 A2-4 99.5 4 — 16 — —— C C 205 A2-5 99.1 4 — 17 42 C 286 C C 207 B1-1 99.6 4 — 17 42 C 268 CC 208 B1-2 99.5 4 — 17 45 C 259 C C 209 B1-3 99.5 4 — 17 44 C 257 C C210 B2-1 99.5 3 — 17 43 C 269 C C 211 B3-1 99.8 5 — 17 39 C 274 B C 212A2-1 102 99.7 3 50 19 41 C 273 C B   212A A2-2 99.3 4 — — 44 C 259 C C214 B1-1 99.8 4 50 19 37 C 287 B C

TABLE 21 Color fastness Direction parallel with Direction orthogonal toHigh rolling direction rolling direction Bending workability temperatureTensile Proof Tensile Proof Good Bad high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm² ) (%) ation) ation)(Evaluation) (Evaluation) 201 A2-1 101 610 568 15 650 582 8 A C A B 202A2-2 616 569 15 645 577 8 A C — — 203 A2-3 623 577 12 655 585 6 B C — —204 A2-4 610 566 14 638 550 7 B C B B 205 A2-5 650 581 8 705 653 3 B C —— 207 B1-1 621 567 14 659 589 8 A C B B 208 B1-2 618 578 14 665 597 7 BC — — 209 B1-3 608 566 15 643 582 8 A C — — 210 B2-1 624 579 13 665 6006 A C B B 211 B3-1 601 554 16 632 569 10 A B B B 212 A2-1 102 620 568 14663 590 7 A C B B   212A A2-2 624 570 12 675 588 7 B C — — 214 B1-1 603557 17 648 580 8 A B B B

TABLE 22 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150° C. × 120 ° C. × Stress corrosion cracking of αgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/mm²) (Evaluation)(Evaluation) 301 C1 103 100 5 — 21 43 C 246 C C   301A C1A 103 99.9 5 —20 45 C 238 C C 302 C1 104 100 5 — 23 49 C 214 C C 303 C1 105 100 3 — 1436 C 302 C C   303A C1A 105 99.7 3 — 14 42 C 276 C C 304 C1 106 100 4 —13 39 C 291 B C 305 C1 107 99.7 4 — 14 43 C 269 B B 306 C1 108 100 2 —20 35 C 296 B C 307 C1 109 99.7 4 — 18 40 C 275 B C   307A C1A 109 99 4— 18 48 C 240 C C 308 C1 110 99.7 4 — 17 45 C 247 C C 309 C1 111 100 6 —23 48 C 215 B C 310 C1 112 100 4 — 20 35 C 286 C C 311 C1 113 99.5 4 —14 42 C 273 B C 312 C1 114 100 4 — 18 41 C 268 B B 313 C1 115 100 5 — 1947 C 235 C C 314 C1 116 99.5 3 — 16 41 C 275 C C 315 C1 117 99.2 4 — 1754 C 209 C C 316 C1 118 99.4 3 — 18 50 C 231 C C 317 C1 119 100 6 — 2433 B 256 A A 318 C1 120 100 1.5 2 18 28 B 357 B B 319 C1 121 100 1.5 217 27 B 359 B B 320 C1 122 100 6 — 21 49 C 214 B C 321 C1 123 100 8 — 2339 C 239 A A 322 C1 124 100 6 — 23 32 B 269 A A 323 C1 125 100 6 — 20 34C 264 A A 324 C1 126 100 2.5 — 19 29 B 339 A B

TABLE 23 Color fastness Direction parallel with Direction orthogonal toHigh rolling direction rolling direction Bending workability temperatureTensile Proof Tensile Proof Good Bad high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm²) (%) ation) ation)(Evaluation) (Evaluation) 301 C1 103 577 536 17 596 545 11 A A C B  301A C1A 103 582 538 16 608 544 8 A B C B 302 C1 104 560 515 18 588532 11 A A C C 303 C1 105 628 578 13 672 603 7 A C B B   303A C1A 105635 582 13 680 607 6 B C B B 304 C1 106 635 583 12 680 610 6 B C B A 305C1 107 631 580 12 677 601 6 B C B B 306 C1 108 604 556 14 644 581 8 A CB B 307 C1 109 608 560 13 656 584 7 A C C C   307A C1A 109 616 561 10667 592 6 B C C C 308 C1 110 600 551 14 642 572 8 A C C B 309 C1 111 554510 18 577 525 13 A A C C 310 C1 112 589 540 17 628 559 9 A C B B 311 C1113 632 580 12 670 598 7 B C C B 312 C1 114 603 560 13 647 577 7 A C A B313 C1 115 591 544 15 630 566 7 A C B B 314 C1 116 620 573 13 662 592 6A C C B 315 C1 117 608 559 14 651 578 7 A C C B 316 C1 118 614 568 13660 585 6 A C C C 317 C1 119 515 473 19 540 483 14 A A C C 318 C1 120651 601 13 718 640 5 B C A A 319 C1 121 643 597 14 706 632 6 A C A A 320C1 122 550 516 18 584 532 12 A A C B 321 C2 123 525 483 18 547 496 13 AA B C 322 C3 124 534 488 16 555 501 12 A A B C 323 C4 125 537 495 17 560504 13 A A B B 324 C5 126 638 582 12 679 610 8 A C A B

TABLE 24 Structure observation Stress relaxation characteristics RatioAverage Precipitate 150 ° C. × 120° C. × Stress corrosion cracking ofαgrain average 1,000 1,000 Effective Stress Test Production Alloy phasesize particle Conductivity hours hours stress W Bending relaxation No.process No. (%) (μm) size (nm) (% IACS) (%) (%) (N/nm²) (Evaluation)(Evaluation) 401 C2 201 100 7 — 28 85 C 58 C C 402 C2 202 100 6 — 29 80C 77 B C 403 C2 203 100 7 — 31 76 C 91 A B 404 C2 204 100 9 — 34 72 C100 A A 405 — 205 100 12 — 12 59 C 189 A A

TABLE 25 Color fastness Direction parallel with Direction orthogonal toHigh rolling direction rolling direction Bending workability temperatureTensile Proof Tensile Proof Good Bad high High strength stress Elon-strength stress Elon- Way Way humidity temperature Test Production AlloyTS_(p) YS_(p) gation TS_(o) YS_(o) gation (Evalu- (Evalu- test test No.process No. (N/mm²) (N/mm²) (%) (N/mm²) (N/mm²) (%) ation) ation)(Evaluation) (Evaluation) 401 C2 201 520 478 15 555 490 10 A B C C 402C2 202 518 480 15 547 487 11 A B C C 403 C2 203 500 472 15 517 473 11 AA C C 404 C2 204 472 445 13 490 450 10 A A C C 405 — 205 635 564 24 665591 16 A B C C

TABLE 26 Structure observation Mechanical strength of the (board)Structure observation seam welded pipe, workability Stress Ratio Average(seam welded pipe) Tensile Proof Flatten- Pipe ex- corrosion ofα grain αβ γ Conduc- strength stress Elon- ing test pansion cracking TestProduction Alloy phase size phase phase phase tivity TS YS gation(Evalu- (Evalu- (Evalu- No. process No. (%) (μm) (%) (%) (%) (% IACS)(N/mm²) (N/mm²) (%) ation) ation) ation) 10 A3-1 1 100 15 100 0 0 17 488392 42 A A A 25 A3-1 2 100 12 100 0 0 15 531 445 36 A A A 40 A3-1 3 10010 100 0 0 16 540 458 37 A A A 55 A3-1 4 100 18 100 0 0 19 470 372 41 AA A 66 A3-1 5 100 15 100 0 0 21 475 366 41 A A A 73 A3-1 6 100 12 100 00 18 512 423 40 A A — 76 A3-1 7 100 10 100 0 0 16 526 440 38 A A A 79A3-1 8 100 12 99.8 0.1 0.1 18 520 433 29 A A B 206 A3-1 101 99.6 10 98.90.7 0.4 17 540 455 30 C C C 213 A3-1 102 99.6 — 99.3 0.6 0.1 19 525 44132 C C C

TABLE 27 Antimicrobial test After high temperature After high Afterfinish high humidity temperature Test Production Alloy rolling test testNo. process No. (Evaluation) (Evaluation) (Evaluation) 5 A2-1 1 A A A 20A2-1 2 A A A 35 A2-1 3 A A A 50 A2-1 4 A A A 61 A2-1 5 A A A 72 A2-1 6 AA A 75 A2-1 7 A A A 78 A2-1 8 A A A 201 A2-1 101 B B — 212 A2-1 102 B —A 401 C2 201 A B B

TABLE 28 Antimicrobial test After high temperature After high Afterfinish high humidity temperature Test Production Alloy rolling test testNo. process No. (Evaluation) (Evaluation) (Evaluation) 10 A3-1 1 A A A25 A3-1 2 A A A 40 A3-1 3 A A A 55 A3-1 4 A A A 73 A3-1 6 A A A 76 A3-17 A A A 206 A3-1 101 B — B 402 C2 202 A B B

From the above evaluation results, regarding the compositions, thecomposition relational expression and the characteristics, the followingwas confirmed.

Due to the fact that all conditions of containing 17 mass % to 34 mass %of Zn, 0.02 mass % to 2.0 mass % of Sn, 1.5 mass % to 5 mass % of Ni,and a balance consisting of Cu and unavoidable impurities, satisfyingrelationships of 12≤f1≤30, 10≤f2≤28, 10≤f3≤33, 1.2≤f4≤4 and 1.4≤f5≤90,and having a metallographic structure in which a ratio of an a phase inthe constituent phase of the metallographic structure is 99.5% or moreby area ratio, and the like were satisfied, a Cu—Zn alloy containing ahigh concentration of Zn and having excellent color fastness, highstrength, good bending workability, satisfactory color fastness, stressrelaxation characteristics and stress corrosion cracking resistance at ahigh temperature and high humidity or at a high temperature was obtained(refer to test Nos. 5, 20, 109, 113 and the like).

Additionally, when the alloy contains Sb, As, P and Al, color fastnessand stress corrosion cracking resistance were further improved (refer totest Nos. 50, 72, 75, 122, 128 to 131 and the like).

Due to the fact that conditions of containing 18 mass % to 33 mass % ofZn, 0.2 mass % to 1.5 mass % of Sn, 1.5 mass % to 4 mass % of Ni, and abalance consisting of Cu and unavoidable impurities, satisfyingrelationships of 15≤f1≤30, 12≤f2≤28, 10≤f3≤30, 1.4≤f4≤3.6 and 1.6≤f5≤12,and having a metallographic structure composed of an α single phase weresatisfied, excellent color fastness, high strength, good bendingworkability, and excellent stress relaxation characteristics wereobtained. Therefore, a Cu—Zn alloy containing a high concentration of Znand having high effective stress in a use environment at a hightemperature, and satisfactory stress corrosion cracking resistance in astate in which stress close to the elastic limit of the material wasloaded and in a state in which high residual stress was present wasobtained (refer to test Nos. 5, 20, 107 and the like).

Additionally, due to the fact that conditions of containing 0.003 mass %to 0.08 mass % of P and satisfying a relationship of 25≤[Ni]/[P]≤750were satisfied, stress relaxation characteristics were further improved,stress corrosion cracking resistance and color fastness were alsoimproved (refer to test Nos. 35, 50, 72 and the like).

When the amount of Zn was more than 34 mass %, bending workability wasdeteriorated and stress relaxation characteristics, stress corrosioncracking resistance and color fastness were deteriorated. When theamount of Zn was less than 17 mass %, strength was lowered and colorfastness was also deteriorated (refer to test Nos. 303, 303A, 304, 317and the like).

When the amount of Ni was less than 1.5 mass %, stress relaxationcharacteristics, stress corrosion cracking resistance and color fastnesswere deteriorated. When the amount of Ni was more than 1.5 mass %,stress relaxation characteristics, stress corrosion cracking resistanceand color fastness were improved (refer to test Nos. 301, 301A, 302,320, 102, 110 and the like).

When the amount of Sn was less than 0.02 mass %, strength was loweredand stress relaxation characteristics were deteriorated. When the amountof Sn was 0.2 mass % or more, strength was increased and color fastnessand stress relaxation characteristics were improved. When the amount ofSn was more than 0.2 mass %, hot workability and bending workabilitywere deteriorated, and stress relaxation characteristics and stresscorrosion cracking resistance were deteriorated. When the amount of Snwas 1.5 mass % or less, hot workability and bending workability wereimpaired, and stress relaxation characteristics and stress corrosioncracking resistance were improved. In Test No. 305, since edge crackingoccurred at the time of hot rolling, the cracked portion was removed andthen the subsequent process was carried out (refer to test Nos. 110,101, 104, 130, 305, 309, 321, 322 and the like).

In the composition relational expression f1=[Zn]+5×[Sn]−2×[Ni], when thevalue was greater than 30, β and γ phases other than an α phase appearedand bending workability, stress relaxation characteristics, stresscorrosion cracking resistance, color fastness and antimicrobialproperties (bactericidal properties) were deteriorated. In addition, itwas found that the value of the composition relational expressionf1=[Zn]+5×[Sn]−2×[Ni] was a boundary value for determining whetherbending workability, stress relaxation characteristics, stress corrosioncracking resistance and color fastness are good or not (refer to testNos. 50, 56, 80, 101 to 105, 307, 307A, 308, 314 to 316 and the like).

In the sheet material, when the ratio of the α phase was less than 99.5%or less than 99.8%, bending workability, stress relaxationcharacteristics, stress corrosion cracking resistance, color fastnessand antimicrobial properties were deteriorated. However, when the ratioof the a phase was 100%, these characteristics were improved and balanceamong tensile strength, proof stress and elongation was good. Further,when the ratio of the α phase was 100%, in samples collected fromdirections parallel with and perpendicular to the rolling direction, theratio of tensile strength in the collection directions, the ratio ofproof stress, and the ratio between tensile strength and proof stress inthe same collection direction were close to 1 (refer to test Nos. 50,56, 80, 101 to 105, 307, 307A, 308, 311, 314 to 316, and the like).

In the seam welded pipe, when the ratio of the α phase in theconstituent phase of the metallographic structure of the original sheetmaterial was less than 99.8%, the ratio of the α phase in themetallographic structure of the seam welded pipe was less than 99.5%,and in a flattening test and a pipe expansion test for the seam weldedpipe, cracking occurred. In addition, stress corrosion crackingresistance was also deteriorated. When the ratio of the α phase was100%, workability and stress corrosion cracking resistance were improvedand tensile strength, proof stress and elongation each had high values(refer to test Nos. 10, 25, 40, 55, 66, 73, 76, 206, 213 and the like).

In the seam welded pipe, even when the ratio of the α phase in theconstituent phase of the metallographic structure of the original sheetmaterial was 100%, the ratio of the α phase in the metallographicstructure of the seam welded pipe was not 100% in some cases. When theratio of the α phase in the metallographic structure of the seam weldedpipe was 99.5% or more, and 0≤2×(γ)+(β)≤0.7, and a metallographicstructure in which a γ phase having an area ratio of 0% to 0.3% and a βphase having an area ratio of 0% to 0.5% are dispsersed in the α phasematrix is provided, in a flattening test and a pipe expansion test forthe seam welded pipe, cracking did not occur. Also, in the seam weldedpipe, the composition relational expression f1=[Zn]+5×[Sn]−2×[Ni] wasimportant and the composition relational expression f1=30 had onethreshold (refer to test Nos. 73, 79, 206, 213 or the like).

When the value of the composition relational expressionf2=[Zn]−0.5×[Sn]−3×[Ni] was greater than 28, stress corrosion crackingresistance were deteriorated. The composition relational expressionf2=28 was a boundary value for determining whether the material couldendure stress corrosion cracking in a severe environment, and as thenumerical value decreased, stress corrosion cracking resistance wasimproved (refer to test Nos. 56, 80, 101, 102, 104, 105, 310, 313 andthe like). In the Cu—Zn alloys shown in Comparative Examples (Test No.401 to 404), stress corrosion cracking was dependant on the amount ofZn. The amount of Zn of about 25 mass % was a boundary content fordetermining whether the material could endure stress corrosion crackingin a severe environment. As a result, the amount of Zn was almost equalto the value of the composition relational expression f2 of 28.

When the value of the composition relational expression f3 was less than10, stress relaxation characteristics were deteriorated. The compositionrelational expression f3=10 was a boundary value for determining whetherstress relaxation characteristics were good or not. The value of thecomposition relational expression f3 was in a range from 10 to 20, asthe value increased. Stress relaxation characteristics were furtherimproved and effective stress at a high temperature was more than 300N/mm² (refer to test Nos. 56, 80, 101 to 104, 106, 106A, 108, 307, 307A,315 and the like).

While color fastness was improved due to the effect of incorporation ofNi and Sn, the value of the composition relational expressionf4=0.7×[Ni]+[Sn] was less than 1.2, and color fastness and stressrelaxation characteristics were deteriorated. When the value of thecomposition relational expression f4 was 1.2 or greater or 1.4 orgreater, color fastness and stress relaxation characteristics werefurther improved (refer to test Nos. 56, 110, 302, 309, 310 and thelike).

When the value of the composition relational expression f5=[Ni]/[Sn] wasless than 1.4, stress relaxation characteristics were deteriorated andbending workability was also deteriorated. When the value of thecomposition relational expression f5 was 1.6 or greater, stressrelaxation characteristics were improved and when the value was 1.8 orgreater, stress relaxation characteristics were further improved. It wasthought that the composition relational expression f5=1.6 had onethreshold for determining whether stress relaxation characteristics weregood or not (refer to test Nos. 312, 103, 67 and the like). In addition,when the value of the f5=[Ni]/[Sn] was greater than 90, stressrelaxation characteristics and color fastness were deteriorated and alsostrength was lowered. When the value of the f5=[Ni]/[Sn] was less than12, stress relaxation characteristics and color fastness were improvedand strength was increased (refer to test Nos. 110, 133, 321, 322 andthe like).

In the case of incorporation of P, when the value of the compositionrelational expression f6=[Ni]/[P] satisfied 25≤f6≤750, or 30≤f6≤500,stress relaxation characteristics were further improved, bendingworkability was not impaired, and stress corrosion cracking resistancewas improved (refer to test Nos. 56, 112, 108, 109, 128, 123, 134, 135,306 and the like).

In addition, precipitates mainly composed of Ni and P, that is,compounds were formed and the average particle size of the precipitateswas 10 nm to 70 nm. Slightly fine grains were formed (refer to test Nos.46 to 60, 118 and the like).

When 0.0005 mass % or more and 0.2 mass % or less in total of at leastone or more selected from Fe, Co, Mg, Mn, Ti, Zr, Cr, Si, Pb and rareearth elements, each contained in an amount of 0.0005 mass % or more and0.05 mass % or less were incorporated, fine grains were obtained andstrength was slightly increased (refer to test Nos. 118 to 127, 132 andthe like). Particularly, even when the contents of Fe and Co were 0.001mass %, fine precipitates were obtained, the average grain size wasreduced, and tensile strength and proof stress were improved.

When the amount of Fe or Co of more than 0.05 mass % was incorporated,the particle size of the precipitates was smaller than 3 nm and theaverage grain size was smaller than 2 μm. Thus, strength was increased,bending workability was deteriorated, and stress relaxationcharacteristics were slightly deteriorated (refer to test Nos. 318, 319and the like).

As shown in Tables 27 and 28, regarding the antimicrobial properties ofthe alloys of the invention, when each additive element was within thecomposition range of the specification and each relational expressionswere satisfied, excellent antimicrobial performance was exhibited.Further, the test pieces after the high temperature high humidity testat 60° C. and a humidity of 95% and the test pieces after the hightemperature test at 120° maintained excellent antimicrobial performance.When the alloys were used for portions of a door knob or the like,touched by hands, and containers or the like, excellent antimicrobialproperties (bactericidal properties) were achieved.

In addition, from the above evaluation results, regarding productionprocesses and characteristics, the following was confirmed.

In actual production facilities, even when the number of annealing timesincluding final annealing was 2 or 3 (processes A1-2, A2-2 and the like)or the method of annealing was a continuous annealing method or a batchtype method (processes A2-1, A2-2 and the like), and the recovery heattreatment was a batch type method carried out in the laboratory or acontinuous annealing method (processes A1-1, A1-2 and the like),strength, bending workability, color fastness, stress relaxationcharacteristics and stress corrosion cracking resistance, which aredesired in the specification, were obtained.

The characteristics obtained from the actual production facilities werethe almost the same as the characteristics of the process B of formingsmall pieces prepared in a laboratory (processes A2-1, B1-1 and thelike).

In the laboratory test of small pieces, when final annealing or arecovery heat treatment was a continuus annealing method or a batch typemethod (processes B1-1 and B1-3), strength, bending workability, colorfastness, stress relaxation characteristics and stress corrosioncracking resistance, which are desired in the specification, wereobtained.

In the small sample pieces of the process B, the characteristics of thealloys of the invention prepared by carrying out annealing one time,carrying out only final annealing without annealing, or repeatedlycarrying out annealing and cold rolling without a hot rolling processwere almost the same (processes B1-1, B2-1 and B3-1).

In addition, when the recovery heat treatment was carried out, stressrelaxation characteristics were improved and the ratio of proofstress/tensile strength was increased and the value was close to 1.0(processes A2-2, A2-4 and the like).

The processes C1 and C1A were carried out by carrying out melting andcasting in a laboratory using facilities of the laboratory, and thefinal heat treatment was a batch type method and a continuous heattreatment method. In the alloys of the invention prepared in bothprocesses, for stress relaxation characteristics, a continuous annealingmethod was more effective but for the other characteristics were almostthe same.

Under the conditions of a heat treatment (300° C.-0.07 minutes) and(250° C.-0.15 minutes) on the assumption of molten Sn plating or thelike, compared to conditions for other recovery heat treatmentsincluding a recovery heat treatment in an actual apparatus, strength waslightly high, and the value of elongation was low, and the values ofstress relaxation characteristics and effective stress at 150° C. weredeteriorated. The target characteristics could be achieved. This heattreatment can be replaced by the recovery heat treatment by carrying outmolten Sn plating or the like, or the recovery heat treatment can beomitted.

The value of the heat treatment conditional expression It1 was high, thefinal working rate was 25% in the processes A2-5 and 2-6, and strengthwas slightly high. However, bending workability and stress corrosioncracking resistance were maintained and were satisfactory.

Regarding stress relaxation characteristics, the case in which finalannealing was carried out by a continuous high temperature short timeannealing method was better compared to the case in which a batch typeannealing method was carried out. Particularly, in the case ofincorporation of P, when annealing was carried out by a high temperatureshort time annealing method, good stress relaxation characteristics wereobtained. In addition, when the index Itl was slightly high,satisfactory stress relaxation characteristics were obtained (processesA1-4, A2-2, A2-5 and A2-7). It was thought that the stress relaxationcharacteristics were affected by balance between Ni and P in the solidsolution state and precipitates of Ni and P.

In the process A2-7 in which the value of Itl was close to the upperlimit, irrespective of a high rolling reduction, compared to the processA2-2, strength was the same or lowered, and stress relaxationcharacteristics were saturated. Bending workability was slightlydeteriorated. In the process A2-8 in which the value of It1 was greaterthan the upper limit, the average grain size was large and irrespectiveof a high rolling reduction, strength was low and the orientation ofmaterial strength was generated. Thus, bending workability, stressrelaxation characteristics and stress corrosion cracking resistance weredeteriorated. In the process A2-9, when the temperature was excessivelyraised by batch type annealing, the grains were enlarged and remarkablemixed grains were formed. Therefore, bending workability wasdeteriorated, the orientation of material strength, that is, the valuesof YS_(P)/TS_(P) and YS_(P)/YS_(O) were smaller than 0.9, and stressrelaxation characteristics and stress corrosion cracking resistance weredeteriorated. In the process A2-10, since the value of It1 was smallerthan a predetermined value, a metallographic structure includinguncrystallized portions was formed. Thus, although strength was high,bending workability, stress relaxation characteristics and stresscorrosion cracking resistance were deteriorated.

There was almost no difference in the recovery heat treatment underbatch type conditions (300° C., holding time: 30 minutes) and continuoushigh temperature short time conditions (450° C.-0.05 minutes) (processesA2-1, A2-2, A1-1, A1-2 and the like).

As described above, when an element such as Ni or Sn are suitably ormost suitably contained in the copper alloy containing a highconcentration of Zn, the alloy can be formed into a sheet material and aseam welded pipe having excellent color fastness, high strength, goodbending workability, satisfactory color fastness, stress relaxationcharacteristics, stress corrosion cracking resistance at a hightemperature and high humidity or at a high temperature, and highantimicrobial performance. Accordingly, excellent cost performance, areduction in thickness and a compact body, which are required in thesedays, can be obtained, and a severe environment including a finalproduct that endures a high temperature and a high humidity, further, amulti-functional final product with high performance and highfunctionality can be obtained. Particularly, when plating is carried outto solve color change or stress corrosion problems, the plating can beomitted and high conductivity or antimicrobial and bactericidalperformance of a copper alloy can be continuously exhibited.Specifically, since strength is high, stress relaxation characteristicsare excellent, and the alloy can endure a severe use environment, thealloy is suitable for connectors, terminals, relays, switches, springs,sockets and the like used in electronic and electric apparatuscomponents and automobile components. In addition, since strength ishigh, the alloy can endure a severe use environment, antimicrobialperformance is high, and the high antimicrobial properties can bemaintained, the alloy is a suitable material for construction metalfittings and members such as handrails, door handles, inner wallmaterials or the like, medical appliances and containers, water supplyand drain facilities, apparatuses and containers, decoration members,and the like.

Further, when conductivity is 14% IACS or more and 25% IACS or less andthe metallographic structure is composed of an a phase, furtherexcellent strength and balance between strength and bending workabilityare obtained and stress relaxation characteristics, particularly,effective stress at 150° C. is increased. Thus, the alloy is a moresuitable material for connectors, terminals, relays, switches, springs,sockets and the like used in electronic and electric apparatuscomponents and automobile components used in a severe environment.

INDUSTRIAL APPLICABILITY

According to the copper alloys of the present invention, excellent costperformance, a small density, and a conductivity higher than theconductivity of phosphorus bronze or nickel silver can be provided andhigh strength, balance between strength and elongation and bendingworkability, stress relaxation characteristics, stress corrosioncracking resistance, color fastness, and antimicrobial properties can beimproved.

1-12. (canceled)
 13. A copper alloy comprising: 20 mass % to 34 mass %of Zn; 0.02 mass % to 2.0 mass % of Sn; 1.5 mass % to 2.0 mass % of Ni;and a balance consisting of Cu and unavoidable impurities, wherein a Zncontent expressed in mass %, [Zn], a Sn content expressed in mass %,[Sn], and a Ni content expressed in mass %, [Ni], satisfy relationshipsof12≤f1≤30, wherein f1=[Zn]+5×[Sn]−2×[Ni],10≤f2≤28,wherein f2=[Zn]−0.3×[Sn]−2×[Ni],10≤f3≤33, wherein f3={f1×(32−f1)×[Ni]}^(1/2); wherein the Sn contentexpressed in mass %, [Sn], and the Ni content expressed in mass %, [Ni],satisfy relationships of1.2≤0.7×[Ni]+[Sn]≤4, and1.4≤[Ni]/[Sn]≤90, wherein a conductivity is 13% IACS or more and 22%IACS or less, and wherein, the copper alloy has a metallographicstructure, selected from the group consisting of (1) a ratio of an αphase in a constituent phase of the metallographic structure is 99.5% ormore by area ratio, and (2) an area ratio of a γ phase (γ)% and an arearatio of a β phase (β)% dispersed in an α phase matrix, satisfy arelationship of 0≤2×(γ)+(β)≤0.7, the γ phase having an area ratio of 0%to 0.3% and the β phase having an area ratio of 0% to 0.5% in the αphase matrix.
 14. A copper alloy comprising: 20 mass % to 34 mass % ofZn; 0.02 mass % to 2.0 mass % of Sn; 1.5 mass % to 2.0 mass % of Ni; atleast one or more selected from 0.003 mass % to 0.09 mass % of P, 0.005mass % to 0.5 mass % of Al, 0.01 mass % to 0.09 mass % of Sb, 0.01 mass% to 0.09 mass % of As, and 0.0005 mass % to 0.03 mass % of Pb; and abalance consisting of Cu and unavoidable impurities, wherein a Zncontent in mass %, [Zn], a Sn content in mass %, [Sn], and a Ni contentin mass %, [Ni] satisfy relationships of12≤f1≤30, wherein f1=[Zn]+5×[Sn]−2×[Ni],10≤f2≤28, wherein f2=[Zn]−0.3×[Sn]−2×[Ni], and10≤f3≤33, wherein f3={f1×(32−f1)×[Ni]}^(1/2); wherein the Sn content inmass %, [Sn],and the Ni content in mass %, [Ni], satisfy relationshipsof1.2≤0.7×[Ni]+[Sn]≤4, and1.4≤[Ni]/[Sn]≤90, wherein a conductivity is 13% IACS or more and 22%IACS or less, and wherein, in a metallographic structure, a ratio of anα phase in a constituent phase of the metallographic structure is 99.5%or more by area ratio or an area ratio of a γ phase (γ)% and an arearatio of a β phase (β)% of an α phase matrix satisfy a relationship of0≤2×(γ)+(β)≤0.7, and the γ phase having an area ratio of 0% to 0.3% andthe β phase having an area ratio of 0% to 0.5% are dispersed in the αphase matrix, wherein, the copper alloy contains P as at least one ormore selected elements, the Ni content expressed in mass %, [Ni] and a Pcontent expressed in mass %, [P] satisfy a relationship of25≤[Ni]/[P]≤750.
 15. A copper alloy comprising: 20 mass % to 34 mass %of Zn; 0.02 mass % to 2.0 mass % of Sn; 1.5 mass % to 2.0 mass % of Ni;0.0005 mass % or more and 0.2 mass % or less in total of at least one ormore selected from Fe, Co, Mg, Mn, Ti, Zr, Cr, Si and rare earth metalelements, each contained in an amount of 0.0005 mass % or more and 0.05mass % or less; and a balance consisting of Cu and unavoidableimpurities, wherein a Zn content expressed in mass %, [Zn], a Sn contentexpressed in mass %, [Sn], and a Ni content expressed in mass %, [Ni],satisfy relationships of12≤f1≤30, wherein f1=[Zn]+5×[Sn]−2×[Ni],10≤f2≤28, wherein f2=[Zn]−0.3×[Sn]−2×[Ni], and10≤f3≤33, wherein f3={f1×(32−f1)×[Ni]}^(1/2); the Sn content expressedin mass %, [Sn], and the Ni content expressed in mass %, [Ni], satisfyrelationships of1.2≤0.7×[Ni]+[Sn]≤4, and1.4≤[Ni]/[Sn]≤90, wherein a conductivity is 13% IACS or more and 22%IACS or less, and wherein, the copper alloy has a metallographicstructure, selected from the group consisting of (1) a ratio of an αphase in a constituent phase of the metallographic structure is 99.5% ormore by area ratio, and (2) an area ratio of a γ phase (γ)% and an arearatio of a β phase (β)% dispersed in an α phase matrix and satisfy arelationship of 0≤2×(γ)+(β)≤0.7, the γ phase having an area ratio of 0%to 0.3% and the β phase having an area ratio of 0% to 0.5% in the αphase matrix.
 16. A copper alloy comprising: 20 mass % to 34 mass % ofZn; 0.02 mass % to 2.0 mass % of Sn; 1.5 mass % to 2.0 mass % of Ni; atleast one or more selected from 0.003 mass % to 0.09 mass % of P, 0.005mass % to 0.5 mass % of Al, 0.01 mass % to 0.09 mass % of Sb, 0.01 mass% to 0.09 mass % of As, and 0.0005 mass % to 0.03 mass % of Pb; 0.0005mass % or more and 0.2 mass % or less in total of at least one or moreselected from Fe, Co, Mg, Mn, Ti, Zr, Cr, Si and rare earth metalelements, each contained in an amount of 0.0005 mass % or more and 0.05mass % or less; and a balance consisting of Cu and unavoidableimpurities, wherein a Zn content expressed in mass %, [Zn], a Sn contentexpressed in mass %, [Sn], and a Ni content expressed in mass %,[Ni],satisfy relationships of12≤f1≤30, wherein f1=[Zn]+5×[Sn]−2×[Ni],10≤f2≤28, wherein f2=[Zn]−0.3×[Sn]−2×[Ni], and10≤f3≤33, wherein f3={f1×(32−f1)×[Ni]}^(1/2); wherein the Sn contentexpressed in mass %, [Sn],and the Ni content expressed in mass %, [Ni],satisfy relationships of1.2≤0.7×[Ni]+[Sn]≤4, and1.4≤[Ni]/[Sn]≤90, wherein a conductivity is 13% IACS or more and 22%IACS or less, and wherein, the copper alloy has a metallographicstructure, selected from the group consisting of (1) a ratio of an αphase in a constituent phase of the metallographic structure is 99.5% ormore by area ratio, and (2) an area ratio of a γ phase (γ)% and an arearatio of a β phase (β)% dispersed in an α phase matrix and satisfying arelationship of 0≤2×(γ)+(β)≤0.7, the γ phase having an area ratio of 0%to 0.3% and the β phase having an area ratio of 0% to 0.5% in the αphase matrix, wherein, when the copper alloy contains P as at least oneor more selected elements, the Ni content in mass %, [Ni], and a Pcontent in mass %, [P], satisfy a relationship of25≤[Ni]/[P]≤750.
 17. The copper alloy according to claim 13, wherein thecopper alloy is applicable to medical appliances, handrails, doorhandles, and water supply and drain sanitary facilities, apparatuses andcontainers.
 18. The copper alloy according to claim 13, wherein thecopper alloy is used for electronic and electrical components andautomobile components of connectors, terminals, relays, and switches.19. The copper alloy according to claim 14, wherein the copper alloy isapplicable to medical appliances, handrails, door handles, and watersupply and drain sanitary facilities, apparatuses and containers. 20.The copper alloy according to claim 15, wherein the copper alloy isapplicable to medical appliances, handrails, door handles, and watersupply and drain sanitary facilities, apparatuses and containers. 21.The copper alloy according to claim 16, wherein the copper alloy isapplicable to medical appliances, handrails, door handles, and watersupply and drain sanitary facilities, apparatuses and containers. 22.The copper alloy according to claim 14, wherein the copper alloy is usedfor electronic and electrical components and automobile components ofconnectors, terminals, relays, and switches.
 23. The copper alloyaccording to claim 15, wherein the copper alloy is used for electronicand electrical components and automobile components of connectors,terminals, relays, and switches.
 24. The copper alloy according to claim16, wherein the copper alloy is used for electronic and electricalcomponents and automobile components of connectors, terminals, relays,and switches.
 25. The copper alloy according to claim 13, wherein the Sncontent expressed in mass %, [Sn], and the Ni content expressed in mass%, [Ni], satisfy relationships of1.6≤0.7×[Ni]+[Sn]≤4, and1.8≤[Ni]/[Sn]≤12, and wherein the conductivity is 13% IACS or more and21% IACS or less.
 26. The copper alloy according to claim 14, whereinthe Sn content expressed in mass %, [Sn], and the Ni content expressedin mass %, [Ni],satisfy relationships of1.6≤0.7×[Ni]+[Sn]≤4, and1.8≤[Ni]/[Sn]≤12, and wherein the conductivity is 13% IACS or more and21% IACS or less.
 27. The copper alloy according to claim 15, whereinthe Sn content expressed in mass %, [Sn], and the Ni content expressedin mass %, [Ni], satisfy relationships of1.6≤0.7×[Ni]+[Sn]≤4, and1.8≤[Ni]/[Sn]≤12, and wherein the conductivity is 13% IACS or more and21% IACS or less.
 28. The copper alloy according to claim 16, whereinthe Sn content expressed in mass %, [Sn], and the Ni content expressedin mass %, [Ni], satisfy relationships of1.6≤0.7×[Ni]+[Sn]≤4, and1.8≤[Ni]/[Sn]≤12, and wherein the conductivity is 13% IACS or more and21% IACS or less.
 29. The copper alloy according to claim 13, whereinthe content of Ni is 1.5 mass % to 2.0 mass %, wherein the conductivityis 13% IACS or more and 21% IACS or less, wherein the Zn contentexpressed in mass %, [Zn], the Sn content expressed in mass %, [Sn], andthe Ni content expressed in mass %, [Ni], satisfy relationships of12≤f1≤29, wherein f1=[Zn]+5×[Sn]−2×[Ni],10≤f2≤27, wherein f2=[Zn]−0.3×[Sn]−2×[Ni], and12≤f3≤33, wherein f3={f1×(32−f1)×[Ni]}^(1/2), and wherein the Sn contentexpressed in mass % [Sn],and the Ni content expressed in mass %, [Ni],satisfy relationships of1.4≤0.7×[Ni]+[Sn]≤4, and1.6≤[Ni]/[Sn]≤90.
 30. The copper alloy according to claim 14: whereinthe copper alloy further includes 0.003 mass % to 0.09 mass % of
 31. Acopper alloy comprising: 20 mass % to 34 mass % of Zn; 0.02 mass % to2.0 mass % of Sn; 1.5 mass % to 2.0 mass % of Ni; 0.0005 mass % to 0.05mass % of Fe; optionally 0.0005 mass % or more and 0.2 mass % or less intotal of one or more selected from Co, Mg, Mn, Ti, Zr, Cr, Si and rareearth metal elements, each contained in an amount of 0.0005 mass % ormore and 0.05 mass % or less; and a balance consisting of Cu andunavoidable impurities, wherein a Zn content expressed in mass %, [Zn],a Sn content expressed in mass %, [Sn], and a Ni content expressed inmass %, [Ni], satisfy relationships of12≤f1≤30, wherein f1=[Zn]+5×[Sn]−2×[Ni],10≤f2≤28, wherein f2=[Zn]−0.3×[Sn]−2×[Ni], and10≤f3≤33, wherein f3={f1×(32−f1)×[Ni]}^(1/2); the Sn content expressedin mass %, [Sn], and the Ni content expressed in mass %, [Ni], satisfyrelationships of1.2≤0.7×[Ni]+[Sn]≤4, and1.4≤[Ni]/[Sn]≤90, wherein a conductivity is 13% IACS or more and 22%IACS or less, and wherein, the copper alloy has a metallographicstructure, selected from the group consisting of (1) a ratio of an αphase in a constituent phase of the metallographic structure is 99.5% ormore by area ratio, and (2) an area ratio of a γ phase (γ)% and an arearatio of a β phase (β)% dispersed in an α phase matrix satisfy arelationship of 0≤2×(γ)+(β)≤0.7, and the γ phase having an area ratio of0% to 0.3% and the β phase having an area ratio of 0% to 0.5% in the αphase matrix.
 32. A copper alloy comprising: 20 mass % to 34 mass % ofZn; 0.02 mass % to 2.0 mass % of Sn; 1.5 mass % to 2.0 mass % of Ni;0.003 mass % to 0.09 mass % of P; 0.0005 mass % to 0.05 mass % of Fe;optionally one or more selected from 0.005 mass % to 0.5 mass % of Al,0.01 mass % to 0.09 mass % of Sb, 0.01 mass % to 0.09 mass % of As, and0.0005 mass % to 0.03 mass % of Pb; optionally 0.0005 mass % or more and0.2 mass % or less in total of one or more selected from Co, Mg, Mn, Ti,Zr, Cr, Si and rare earth metal elements, each contained in an amount of0.0005 mass % or more and 0.05 mass % or less; and a balance consistingof Cu and unavoidable impurities, wherein a Zn content expressed in mass%, [Zn], a Sn content expressed in mass %, [Sn], and a Ni contentexpressed in mass %, [Ni], satisfy relationships of12≤f1≤30, wherein f1=[Zn]+5×[Sn]−2×[Ni],10≤f2≤28, wherein f2=[Zn]−0.3×[Sn]−2×[Ni], and10≤f3≤33, wherein f3={f1×(32−f1)×[Ni]}^(1/2); wherein the Sn contentexpressed in mass %, [Sn], and the Ni content expressed in mass %, [Ni],satisfy relationships of1.2≤0.7×[Ni]+[Sn]≤4, and1.4≤[Ni]/[Sn]≤90, wherein a conductivity is 13% IACS or more and 22%IACS or less, and wherein, the copper alloy has a metallographicstructure, selected from the group consisting of (1) a ratio of an αphase in a constituent phase of the metallographic structure is 99.5% ormore by area ratio, and (2) an area ratio of a γ phase (γ)% and an arearatio of a β phase (β)% dispersed in an α phase matrix satisfy arelationship of 0≤2×(γ)+(β)≤0.7, and the γ phase having an area ratio of0% to 0.3% and the β phase having an area ratio of 0% to 0.5% in the αphase matrix, wherein the Ni content expressed in mass %, [Ni], and a Pcontent expressed in mass %, [P], satisfy a relationship of25≤[Ni]/[P]≤750.
 33. The copper alloy according to claim 13: whereinproof stress×80%×(100%−stress relaxation rate (%) at 150° C. for 1,000hours) is 295 N/mm² or more.
 34. The copper alloy according to claim 14:wherein proof stress×80%×(100%−stress relaxation rate (%) at 150° C. for1,000 hours) is 295 N/mm² or more.
 35. The copper alloy according toclaim 15: wherein proof stress×80%×(100%−stress relaxation rate (%) at150° C. for 1,000 hours) is 295 N/mm² or more.
 36. The copper alloyaccording to claim 16: wherein proof stress×80%×(100%−stress relaxationrate (%) at 150° C. for 1,000 hours) is 295 N/mm² or more.